Microscope Slide Peak Power Sensor for Two-Photon Lasers


  • Measure Relative Peak Power of Two-Photon Lasers
  • Compatible with Microscope Stages for Measurements at the Sample
  • Designed to Optimize Pulses for Multiphoton Imaging
  • Compatible with Dry, Water Immersion, and Oil Immersion Objectives

NS170C

Microscope Slide Peak Power Sensor for Two-Photon Lasers, 780 - 1300 nm

NS170C Microscope Slide Peak Power Sensor used with a Prelude® Imaging Microscope and TL10X-2P Objective

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Key Specifications
Detector Type Second-Order Nonlinear Crystal
with Silicon Photodiode
Laser Wavelength Range 780 - 1300 nm
SHG Wavelength Range 390 - 650 nm
Max Peak Power Densitya 10 TW/cm2
Laser Average Power Rangeb 0.5 - 350 mW
SHG Optical Power Working Range 10 nW - 5 mW
Resolutionc 1 nW
  • The specified damage threshold is for objectives with NA > 0.5. The damage threshold will be lower for NA < 0.5.
  • The working range provided is for lasers with a repetition rate of 80 MHz. Because the peak power and peak power density are dependent on the average power and repetition rate of the laser, the upper limit to the working average power range will be lower for lower repetition rates. Exceeding the maximum average power may result in damage to the sensor's optical components.
  • Resolution of the measured SHG signal measured with a PM100D console in low bandwidth setting.
Laser Pulse Optimization at the Focus of a Microscope using the NS170C Sensor
(See Applications Tab for Details)

Features

  • Designed to Measure Relative Peak Power of Two-Photon Lasers
  • Nonlinear Crystal Enables Direct Measurement of the Laser's Second Harmonic
    • Laser Wavelength Range: 780 - 1300 nm
    • Second-Harmonic Wavelength Range: 390 - 650 nm
  • Footprint Enables Peak Power Optimization at the Sample Plane
  • Compatible with Dry, Water Immersion, and Oil Immersion Objectives
  • Compatible with Thorlabs' Power Meter Consoles (Sold Below)

Applications

  • Optimize Group Delay Dispersion of Femtosecond Lasers at the Focus of a Two-Photon Microscope
  • Ensure Laser Conditions are Consistent Between Experiments
  • Quickly Evaluate the Quality of Femtosecond Laser Pulses

Thorlabs' Microscope Slide Peak Power Sensor is designed to measure the relative peak power of two-photon lasers. It shares the same physical dimensions as a microscope slide, enabling measurements of the relative peak power at the focus of a microscope and making the sensor ideal for laser pulse optimization for multiphoton microscopy (see the Applications tab for details).

The NS170C sensor utilizes a second-order nonlinear β-BBO (beta-BaB2O4) crystal to convert incident ultrafast near-infrared (NIR) pulses into their visible second harmonic. Because the efficiency of second harmonic generation (SHG) is proportional to the peak power density, or peak intensity, of the NIR femtosecond pulses, the magnitude of the detected second harmonic light provides a relative measurement of the peak power of the laser. Please see the Optical Design and Operation tabs for more details.

The NS170C sensor is compatible with microscope slide holders of standard upright and inverted microscopes. As illustrated in the animation to the right, the sensor can be used to measure the relative peak power at the focus of a microscope. This allows the user to optimize the laser pulse duration directly at the sample plane for high image contrast (see the Applications tab for details). The sensor is also post-mountable via an 8-32 (M4 x 0.7) tapped hole, allowing for the relative peak power to be measured in an optical set-up of standard optomechanical components.

The housing of the NS170C sensor features a knurled adjustment wheel to tune the angle between the light's polarization orientation and the β-BBO crystal's optical axis. At the entrance of the sensor is a 170 µm thick cover glass sealed to the sensor housing, allowing the sensor to be used with dry, water immersion, and oil immersion objectives. The working distance from the top of the cover glass to the β-BBO crystal is 0.22 mm. The bottom of the sensor housing features a laser-engraved alignment crosshair that marks the active sensor area to aid in aligning and focusing the beam. To use, insert the housing into the beam path such that the engraved side is facing the objective of your microscope. Once the beam is centered on the engraved target, simply turn the sensor over so that the detector is facing the beam in order to take a power measurement.

Second Harmonic Generation
The efficiency of SHG is dependent on the peak power density of incident laser pulses. Once the sensor is positioned at the focal plane of the microscope objective, the effective focal area becomes fixed and the SHG signal is only dependent on peak power. For a given average laser power and repetition rate, the peak power is only dependent on the pulse duration. Therefore, changes to the pulse duration results in a clear metered readout of the SHG power, allowing for optimization of laser pulses directly at the sample plane. Please see the Operation tab for a detailed description of how these parameters impact the SHG conversion efficiency. 

NS170C Top ViewClick to Enlarge
The NS170C sensor features a knurled phase adjustment wheel to tune the rotational orientation of the β-BBO crystal.

Power Meter Console and Interface Compatibility
The NS170C sensor is compatible with the PM100D, PM100APM400, and PM5020 power meter consoles, as well as many of our C-series power and energy meter interfaces, which provide communication between the sensor and an external control unit such as a PC. A 1.5 m cable attached to the side of the sensor head leads to a D-sub 9-pin male connector. Nonvolatile memory in the sensor connector contains sensor information data and the NIST- and PTB- traceable calibration data. Please note that the NIST and PTB calibration is for the visible light incident on the detector; however, the magnitude of that visible light is specific to the illumination conditions of the NIR femtosecond pulses. Please see the Applications tab for more details.

When using the NS170C sensor with our power meter consoles and interfaces, please use the NIR input laser wavelength as the source wavelength.

Recalibration Service
Recalibration services are available for our power sensors and power meter consoles. We recommend your Thorlabs sensor and console be recalibrated as a pair; however, each may be recalibrated individually. Recalibration of a single-channel power and/or energy meter console or interface is included with the CAL-NS Microscope Slide Peak Power Sensor Recalibration Service below at no additional cost. We recommend yearly recalibration to ensure accuracy and performance. For more information, please contact please contact Tech Support

NS170C Specifications
Detector Type Second-Order Nonlinear Crystal with Silicon Photodiode
Laser Wavelength Range 780 - 1300 nm
SHG Wavelength Range 390 - 650 nm
Max Peak Power Densitya 10 TW/cm2
Laser Average Power Rangeb 0.5 - 350 mW
SHG Optical Power Working Range 10 nW - 5 mW
Responsivity (Click for Plot) Typical Responsivity
Click Here for Raw Data
Input Aperture Ø4.5 mm
Working Distance 0.22 mm
Linearityc ±0.5%
Resolutionc,d 1 nW
Measurement Uncertaintyc,e ±3% (440 - 650 nm)
±5% (390 - 439 nm)
Response Time <1 µs
Typical Application GDD Optimization of a Femtosecond Laser at the Focus of a Two-Photon Microscopef
Sensor Dimensions Base: 76.0 mm x 25.2 mm x 5.0 mm (2.99" x 0.99" x 0.20")
Overall: 76.0 mm x 30.0 mm x 11.0 mm (2.99" x 1.18" x 0.43")
Cable Length 1.5 m
Connector Sub-D 9 Pin Male
Weight 80 g
Post Mounting Combi Thread 8-32 and M4
Compatible Consolesg PM100D, PM100A, PM400, and PM5020
Compatible Interfacesg PM101, PM101A, PM101R, PM101U, PM103, PM103A, PM103EPM103U, and PM100USB
  • The specified damage threshold is for objectives with NA > 0.5. The damage threshold will be lower for NA < 0.5.
  • The working range provided is for lasers with a repetition rate of 80 MHz. Because the peak power and peak power density are dependent on the average power and repetition rate of the laser, the upper limit to the working average power range will be lower for lower repetition rates. Exceeding the maximum average power may result in damage to the sensor's optical components.
  • This specification is for the measured SHG signal.
  • Measured with a PM100D console in low bandwidth setting.
  • Valid for 1/e2 beam diameters >1 mm at the photodiode sensor. Please note that the photodiode sensor is several millimeters below the β-BBO crystal and for high NA objectives, the beam diameter is expanded appreciably.
  • Please see the Application tab for more details.
  • The NS170C sensor is compatible with all currently available photodiode power meter consoles and interfaces, as well as the previous-generation PM200 and PM320E consoles; it is not compatible with other previous generation Thorlabs power meter consoles.

Sensor Connector

D-type Male

DB9 Male

Pin Pin Connections
1 Not Used
2 EEPROM Data
3 Photodiode Anode Ground
4 Photodiode Cathode
5 Not Used
6 EEPROM Ground
7 Not Used
8 Not Used
9 Not Used

Cleaning
The housing of the NS170C sensor head can be cleaned using a soft damp cloth. The integrated glass sensor cover of the NS170C sensors can be cleaned with appropriate solvents like isopropanol.

Calibration
The calibration of the sensors should remain stable for over a year provided that the unit has not been exposed to excessive optical powers. We recommend yearly recalibration to ensure accuracy and performance, which may be ordered using the CAL-NS item number below. Please contact Tech Support for assistance.

For more details on the graphs below, please see the Operation tab.

NS170C Filter TransmissionClick to Enlarge
Click Here for Raw Data
Optical filters underneath the β-BBO crystal reject NIR light, allowing only visible second harmonic light to transmit to the silicon photodiode. The blue highlighted regions denote the opertating input laser wavelength range (780 - 1300 nm) and converted SHG wavelength range (390 - 650 nm). 
NS170C Focal PositionClick to Enlarge
Click Here for Raw Data
Normalized SHG signal of the NS170C power sensor as a function of the microscope objective focal position. Data was collected using an objective with NA = 0.5. The blue highlighted region represents the 30 μm thickness of the β-BBO crystal where the light must be focused in order for appreciable SHG conversion to occur.
NS170C GDD CompensationClick to Enlarge
Click Here for Raw Data
Normalized SHG signal of the NS170C power sensor as a function of applied group delay dispersion (GDD). Data was collected for a TIBERIUS tunable Ti:Sapphire laser centered at 800 nm with 100 fs pulses, and the dispersion was adjusted using an FSPC pulse compressor. 
NS170C SHG Signal Dependence on Microscope NAClick to Enlarge
Click Here for Raw Data
Power of the converted SHG signal as a function of the microscope objective NA. The average laser power through the objective was held constant at 100 mW for each measurement. The spatial frequency acceptance bandwidth of the bulk β-BBO crystal is approximately equal to 0.25 NA. Objectives with an NA much larger than 0.25 will have a reduction in the amount of generated SHG signal. 
NS170C SHG Signal Dependence on Laser PowerClick to Enlarge
Click Here for Raw Data
Power of the converted SHG signal as a function of the input laser's average power. Data was collected for an input laser centered at 950 nm with 56 fs pulses.
NS170C Optical DesignClick to Enlarge
An illustration to show the optical design of the NS170C Microscope Slide Peak Power Sensor. An ultrathin β-BBO crystal is used to convert femtosecond NIR laser pulses into their visible second harmonic. Shortpass filters reflect the residual NIR light, allowing only the visible second harmonic light to transmit to the silicon photodiode sensor. 

Nonlinear Crystal with Silicon Photodiode Sensor

The NS170C Microscope Slide Peak Power Sensor was designed to measure the relative peak power of two-photon lasers. As shown in the diagram to the right, the sensor features a 30 µm ultrathin β-BBO crystal that converts incident femtosecond NIR pulses (780 – 1300 nm) into their second harmonic (390 – 650 nm). Shortpass filters underneath the β-BBO crystal reject the residual NIR light, allowing only the visible second harmonic light to transmit down to the large area silicon photodiode sensor (see Graphs tab). 

A microscope objective is shown focusing the femtosecond NIR pulses into the β-BBO crystal through a Ø4.5 mm entrance aperture. Because the SHG process requires high peak intensities, the sensor only generates detectable second harmonic light when the ultrathin β-BBO crystal is in the focus of the objective. This means the NS170C sensor is sensitive to the peak power density of the focused femtosecond pulses rather than the average power; therefore, the detected SHG signal can be used as a relative measurement of the lasers' peak intensity. For more details on the generation of second harmonic light using β-BBO crystals, please see the SHG Tutorial tab.

At the top of the NS170C sensor is a standard 170 µm thick cover glass that is sealed to the housing, allowing it to be used with dry, water immersion, and oil immersion objectives. The immersion media can be placed directly on the surface of the cover glass without damaging the sensor. The working distance from the top of the cover glass to the β-BBO crystal is 0.22 mm. Between the cover glass and the β-BBO crystal is an 80 μm air-gap, which is necessary because epoxy or index-matching gel would burn in the focus of the high-intensity femtosecond pulses. While this air-gap causes total internal reflection (TIR) of the highest spatial frequencies when using high NA objectives, the second harmonic process in the β-BBO crystal has a finite spatial frequency acceptance bandwidth, which is exceeded by high NA objectives. Therefore, the highest spatial frequencies rejected by TIR would not appreciably contribute to the SHG process.

The housing of the NS170C sensor shares dimensions with a microscope slide and can fit on standard microscope stages, allowing for measurements of the relative peak power at the focus of a microscope (see Applications tab for details). 

Operation

To enhance the efficiency of SHG while using the NS170C sensor, several experimental parameters should be taken into consideration and are described briefly below. For a more detailed description of nonlinear optics and the generation of second harmonic light, please see the SHG Tutorial tab. 

  • Peak Power: As shown mathematically below, the peak power of the fundamental input laser is dependent on the average power, repetition rate, and pulse duration, thereby influencing the SHG conversion efficiency (see Figure 1 below). Please see the Performance tab for examples of the NS170C sensor's typical performance under various experimental conditions.
  • Focal Area: The generation of second harmonic light requires high peak intensities for efficient conversion; therefore, it is typically necessary to focus incident laser light in the SHG crystal. Due to the direct relationship between the crystal's thickness and the recommended focal spot size, the ultrathin 30 μm β-BBO crystal used in the NS170C sensor requires a microscope objective to tightly focus the incident laser light in the crystal. The efficiency of the SHG process decreases substantially as the incident beam diverges from its focus since the pulse energy is distributed across a larger area (see Figure 2 below). Additionally, because the β-BBO crystal has a thickness of 30 µm, the optimum longitudinal position of the focused light is <30 μm in depth. The converted second harmonic light is therefore observed as a brief “flash” in the power meter readout, and focal adjustments should be performed slowly.
  • Numerical Aperture: The spatial frequency acceptance bandwidth of the bulk β-BBO crystal in the NS170C sensor is approximately equal to an NA of 0.2. Objectives with numerical apertures much larger than 0.2 will have a reduction in the amount of generated SHG signal and therefore a smaller reported SHG power (see Figure 3 below). It is important to note that the reduced signal with higher NA objectives does not reduce the utility of the device in optimizing the system for maximum imaging performance. This non-intuitive behavior is a limitation of SHG in macroscopic bulk crystals and not an indication that a higher NA objective produces less two-photon absorption or second- and third-harmonic generation from microscopic targets.
  • Group Delay Dispersion: β-BBO crystals generate second harmonic light from ultrafast lasers with femtosecond pulse durations. Pulse broadening from group delay dispersion (GDD) occurs as the pulse propagates through optical elements, resulting in a decrease in peak power. Femtosecond Pulse Compressors are used to compensate for the system GDD, making the pulse duration as short as possible (see Figure 4 below). Ideally, the GDD should be optimized after the pulse propagates through all optical elements to ensure the highest peak power, and peak intensity, at the sample. With the integrated cover glass and 0.22 mm working distance, the NS170C sensor allows for GDD optimization directly at the sample plane by simply tuning the GDD while monitoring the SHG output.
  • Phase Matching: The SHG process is sensitive to the linear polarization orientation of the incident NIR laser pulses.The knurled phase adjustment wheel on the NS170C sensor housing can be used to tune the angle between the light's polarization orientation and the β-BBO crystal's optical axis, which can provide a 10X enhancement in SHG signal and increase the signal-to-noise ratio. The wheel should be adjusted such that the angle indicator is parallel with the laser polarization state; if the polarization state is unknown, the wheel can be tuned while monitoring the SHG signal to maximize the output. 
  • Orientation: Degree level changes to the pitch, roll, and yaw of the sensor relative to the incident light can cause changes to the shape of the sensor’s responsivity. Under typical laboratory conditions, the orientation of the sensor can be adjusted by-hand to optimize the SHG signal level; however, users should note that an optimization routine is necessary to establish long-term system performance data or global maximum SHG readings. It is therefore recommended to use a level when mounting the NS170C sensor to ensure consistency in the sensor’s orientation. For singular pulse optimization tasks, less care is necessary in pitch/roll optimization, as the peak power readout through the SHG signal on the power meter will respond appropriately even if it is not the global best orientation.
NS170C SHG Signal Dependence on Laser PowerClick to Enlarge
Click Here for Raw Data
Figure 1: Power of the converted SHG signal as a function of the input laser's average power. Data was collected for an input laser centered at 950 nm with 56 fs pulses.
NS170C Focal PositionClick to Enlarge
Click Here for Raw Data
Figure 2: Normalized SHG signal of the NS170C power sensor as a function of the microscope objective focal position. Data was collected using an objective with NA = 0.5. The blue highlighted region represents the 30 μm thickness of the β-BBO crystal where the light must be focused in order for appreciable SHG conversion to occur.
NS170C SHG Signal Dependence on Microscope NAClick to Enlarge
Click Here for Raw Data
Figure 3: Power of the converted SHG signal as a function of the microscope objective NA. The average laser power through the objective was held constant at 100 mW for each measurement. The spatial frequency acceptance bandwidth of the bulk β-BBO crystal is approximately equal to 0.25 NA. Objectives with an NA much larger than 0.25 will have a reduction in the amount of generated SHG signal.
NS170C GDD CompensationClick to Enlarge
Click Here for Raw Data
Figure 4: Normalized SHG signal of the NS170C power sensor as a function of applied group delay dispersion (GDD). Data was collected for a TIBERIUS tunable Ti:Sapphire laser centered at 800 nm with 100 fs pulses, and the dispersion was adjusted using an FSPC pulse compressor. 

Parameters and Constants
Aeff Effective Focal Area
c Speed of Light in Vacuum
deff χ2 Tensor Term for Mediating SHG Process
Δk Phase Matching Parameter
ε0 Vacuum Electric Permittivity
E Pulse Energy
frep Repetition Rate
L Length of Nonlinear Crystal
n1 Index of Refraction for Fundamental Laser
n2 Index of Refraction for SHG
ηSHG SHG Efficiency
Pavg Average Power of Fundamental Laser
Ppeak Peak Power of Pulse
PSHG Power of SHG Signal
τ Pulse Duration
ω1 Optical Angular Frequency of Fundamental Laser

Theory of Operation

The derivation below shows how the NS170C power sensor uses output SHG signal to provide a relative measure of the fundamental laser’s peak power. For a more detailed description of nonlinear optics and the generation of second harmonic light, please see the SHG Tutorial tab. The power of converted SHG signal is defined by

where ηSHG is the efficiency of SHG and Pavg is the average power of the fundamental laser. Using a plane wave model and assuming a simple Gaussian pulse intensity profile,* the efficiency of SHG for input intensity can be defined as

Please see the table to the right for a full list of parameters. Equation (2) yields the relationship

where Ppeak is the peak power of the fundamental laser and Aeff is the effective focal area of the laser spot focused inside the nonlinear crystal. By substitiuting Equation (3) into Equation (1), the power of converted SHG signal can be represented by

Thus, the power of converted SHG signal is dependent on the peak power of the fundamental laser. The peak power is given by

where E is the pulse energy (defined by E = Pavg /frep), frep is the repetition rate, and τ is the pulse duration of the fundamental laser. Substituting Equation (5) into Equation (4), the power of converted SHG signal can be written as

Therefore, the power of output SHG signal is dependent on the average power, repetition rate, and pulse duration of the fundamental laser, in addition to the focal spot size inside the nonlinear crystal used for SHG. 

*A. Yariv and P. Yeh, Optical Waves in Crystals, New York: John Wiley & Sons, 2002, pp. 516-530.

Typical Applications

The NS170C Microscope Slide Peak Power Sensor allows for the relative peak power of two-photon lasers to be measured at the focus of a microscope by utilizing a β-BBO crystal to convert the laser pulses to their second harmonic. Because the efficiency of SHG is proportional to the peak power of the NIR femtosecond pulses, the magnitude of the detected second harmonic light allows for quantitative feedback on the pulses and enables optimization of the experimental system. Below are three typical applications of the NS170C sensor.

Laser Pulse Optimization at the Focus of a Microscope using the NS170C Sensor

Example 1: Optimize Pulse Duration at the Focus of a Microscope

In multiphoton microscopy, pulse broadening from group delay dispersion (GDD) occurs when ultrafast laser pulses propagate through the optical elements in the microscope, resulting in poor image contrast. Femtosecond Pulse Compressors compensate for GDD imparted by the microscope on the laser pulse, ensuring that the pulse arriving at the sample is as short as possible. Because the NS170C sensor shares the same dimensions as a microscope slide and is compatible with most upright and inverted microscope stages, the laser pulse GDD can be optimized directly at the sample plane by simply monitoring the SHG signal output.

The animation here illustrates how the NS170C sensor can be used to optimize the pulse duration of femtosecond laser pulses at the focus of a microscope. The sensor is mounted to a Bergamo® II Multiphoton Imaging Microscope and is connected to a PM400 Optical Power Meter Console to measure the second harmonic signal of femtosecond pulses from a Tiberius® Tunable Ti:Sapphire Laser; an FSPC Femtosecond Pulse Compressor is used to adjust the GDD. The pulse duration at the microscope focus can be optimized using the following procedure:

  1. Find the focus of the microscope by adjusting the objective position while monitoring the output SHG signal on the power meter. The optimal objective position is reached when the SHG signal is maximized. To minimize the possibility of damaging a component, it is recommended to start with the sensor below the focus and slowly bringing the objective down (or the sensor up) until the beam is focused in the β-BBO crystal. Because the thickness of the β-BBO crystal is 30 µm, the power change during focal position optimization is observed as a brief “flash” in the SHG signal. Adjustments to the objective position should be done slowly as to not miss this "flash" in signal.
  2. Tune the orientation of the β-BBO crystal by adjusting the wheel on the NS170C sensor while monitoring the output SHG signal on the power meter. The optimal crystal position is reached when the SHG signal is maximized.
  3. Tune the GDD of the FSPC pulse compressor by rotating the knob on the side of the unit while monitoring the output SHG signal on the power meter. The optimal pulse duration is reached when the SHG signal is maximized.

Example 2: Ensure Consistent Laser Conditions Between Measurements

The NS170C sensor can be used to ensure day-to-day consistency in experimental conditions; however, degree level changes to the pitch, roll, and yaw of the sensor relative to the incident light can cause changes to the shape of the sensor’s responsivity (see Specs tab for details). Under typical laboratory conditions, the orientation of the sensor can be adjusted by-hand to optimize the SHG signal level; however, users should note that an optimization routine is necessary to establish long-term system performance data or global maximum SHG readings. It is therefore recommended to use a level when mounting the NS170C sensor to ensure consistency in the sensor’s orientation. For singular pulse optimization tasks, less care is necessary in pitch/roll optimization, as the peak power readout through the SHG signal on the power meter will respond appropriately even if it is not the global best orientation.

Example 3: Quickly Evaluate the Quality of Femtosecond Laser Pulses

Knowing the typical performance of the NS170C sensor under various experimental conditions can be a useful reference when evaluating the output SHG signal (see Performance tab for details). By comparing the measured SHG signal with the expected performance for a given experiment, the NS170C sensor can quickly and clearly provide feedback on the quality of femtosecond laser pulses that a frequency-resolved optical gating (FROG) measurement would provide. For example, a femtosecond laser that erroneously has picosecond pulses will result in an SHG power orders of magnitude lower than expected. Please see Example 2 above for details on the importance of orientation when using the NS170C sensor as a measure of the systems performance.

Second Harmonic Generation and Phase Matching

Optimizing the intensity and beam quality of the second harmonic light provided by these β-BBO crystals requires choosing the crystal thickness appropriate to the duration of the input laser pulses, determining a focal spot size that balances the positive and negative effects of the focal region, and optimizing the phase matching conditions. Succinct guidance on each of these topics is provided by the graphs available on the Specs tab. Additional information and background, which can be helpful for interpreting the graphed data as well as more effectively using the crystals to generate second harmonic light, is included in the expandable sections below.

Click on a question to expand the corresponding passage that provides an answer, and then click again to contract the section. Answers to questions lower in the list reference the discussions in preceding sections.

Pulsed Laser Emission: Power and Energy Calculations

Determining whether emission from a pulsed laser is compatible with a device or application can require referencing parameters that are not supplied by the laser's manufacturer. When this is the case, the necessary parameters can typically be calculated from the available information. Calculating peak pulse power, average power, pulse energy, and related parameters can be necessary to achieve desired outcomes including:

  • Protecting biological samples from harm.
  • Measuring the pulsed laser emission without damaging photodetectors and other sensors.
  • Exciting fluorescence and non-linear effects in materials.

Pulsed laser radiation parameters are illustrated in Figure 1 and described in the table. For quick reference, a list of equations are provided below. The document available for download provides this information, as well as an introduction to pulsed laser emission, an overview of relationships among the different parameters, and guidance for applying the calculations. 

 

Equations:

Period and repetition rate are reciprocal:    and 
Pulse energy calculated from average power:       
Average power calculated from pulse energy:        
Peak pulse power estimated from pulse energy:            

Peak power and average power calculated from each other:
  and
Peak power calculated from average power and duty cycle*:
*Duty cycle () is the fraction of time during which there is laser pulse emission.
Pulsed Laser Emission Parameters
Click to Enlarge

Figure 1: Parameters used to describe pulsed laser emission are indicated in the plot (above) and described in the table (below). Pulse energy (E) is the shaded area under the pulse curve. Pulse energy is, equivalently, the area of the diagonally hashed region. 

Parameter Symbol Units Description
Pulse Energy E Joules [J] A measure of one pulse's total emission, which is the only light emitted by the laser over the entire period. The pulse energy equals the shaded area, which is equivalent to the area covered by diagonal hash marks.
Period Δt  Seconds [s]  The amount of time between the start of one pulse and the start of the next.
Average Power Pavg Watts [W] The height on the optical power axis, if the energy emitted by the pulse were uniformly spread over the entire period.
Instantaneous Power P Watts [W] The optical power at a single, specific point in time.
Peak Power Ppeak Watts [W] The maximum instantaneous optical power output by the laser.
Pulse Width Seconds [s] A measure of the time between the beginning and end of the pulse, typically based on the full width half maximum (FWHM) of the pulse shape. Also called pulse duration.
Repetition Rate frep Hertz [Hz] The frequency with which pulses are emitted. Equal to the reciprocal of the period.

Example Calculation:

Is it safe to use a detector with a specified maximum peak optical input power of 75 mW to measure the following pulsed laser emission?

  • Average Power: 1 mW
  • Repetition Rate: 85 MHz
  • Pulse Width: 10 fs

The energy per pulse:

seems low, but the peak pulse power is:

It is not safe to use the detector to measure this pulsed laser emission, since the peak power of the pulses is >5 orders of magnitude higher than the detector's maximum peak optical input power.


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Microscope Slide Peak Power Sensor for Two-Photon Lasers

NS170C Optical DesignClick to Enlarge
The back of the NS170C housing is engraved with the sensor specifications and a target for centering the beam on the sensor.
  • Utilizes a β-BBO Crystal to Measure the Relative Peak Power of Two-Photon Lasers
    • Laser Wavelength Range: 780 - 1300 nm
    • Second-Harmonic Wavelength Range: 390 - 650 nm
  • Ideal for Optimizing Laser Conditions at the Sample Plane of a Microscope
  • Compatible with Dry, Water Immersion, and Oil Immersion Objectives
  • Yearly Recalibration with CAL-NS Recalibration Service Recommended (For More Information, Contact Tech Support)

The NS170C Microscope Slide Peak Power Sensor is designed to measure the relative peak power of lasers for multiphoton microscopy. It can be used with femtosecond lasers with center wavelengths from 780 nm to 1300 nm. To avoid damaging the optical components, the maximum average power should not exceed 350 mW. The damage threshold for the peak power density is 10 TW/cm2 at 80 MHz repetition rate and for microscope objectives with NA > 0.5; the damage threshold will be lower for NA < 0.5. The photodiode sensor can detect SHG light with wavelengths from 390 nm to 650 nm at optical powers from 10 nW to 5 mW. Please see the Specs tab for more information.

The converted SHG signal of the NS170C peak power sensor is highly dependent on the experimental conditions (see Operation tab for details). The wavelength, pulse duration, quality of the temporal pulse profile, repetition rate, and power of the NIR input laser in addition to the objective numerical aperture and immersion all contribute to the magnitude of the converted visible SHG signal. The table below describes the typical performance of the NS170C peak power sensor under various experimental conditions and can be used as a reference when evaluating the expected SHG signal for a given experiment. 

Thorlabs recommends yearly recalibration of the NS170C sensor. Thorlabs offers a recalibration service for this photodiode sensor, which can be ordered below (Item # CAL-NS). Recalibration of a single-channel power and/or energy meter console or interface is included with the recalibration of a sensor at no additional cost. For more information, please contact Tech Support

NS170C Optical DesignClick to Enlarge
The NS170C sensor may be post mounted via the 8-32 (M4 x 0.7) tap in the side of the housing.
NS170C Typical Performancea
Immersion Laser Power at Sampleb Wavelength Pulse Duration Objective SHG Signal
Air 100 mW 780 nmc 80 fs 20X, 0.5 NAf 980 µW
800 nmc 100 fs 1100 µW
900 nmc 960 µW
920 nmd 150 fs 10X, 0.3 NAg 216 µW
920 nme 10X, 0.5 NAh 580 µW
1000 nmc 180 fs 20X, 0.5 NAf 400 µW
350 mW 800 nmc 100 fs 5500 µW
Water 100 mW 800 nmc 100 fs 40X, 0.8 NAi 255 µW
  • This table is only to be used as a reference guide. Please see the Specs tab for full performance specifications.
  • The laser power measured out of the objective.
  • A Tiberius® tunable Ti:Sapphire laser was used for this measurement.
  • A commercial 920 nm fixed laser with 80 MHz repetition rate and <100 fs transform limited pulses was used for this measurement.
  • A commercial 920 nm fixed laser with 80 MHz repetition rate and <150 fs transform limited pulses was used for this measurement.
  • Olympus Plan Fluorite 20X Objective, 0.5 NA (Item # RMS20X-PF)
  • Nikon Plan Fluorite 10X Objective, 0.3 NA (Item # N10X-PF)
  • Thorlabs Apochromatic 10X Objective, 0.5 NA (Item # TL10X-2P)
  • Nikon Apochromatic 40X Objective, 0.8 NA (Item # N40X-NIR)
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NS170C Support Documentation
NS170CNEW!Microscope Slide Peak Power Sensor for Two-Photon Lasers, 780 - 1300 nm
$2,650.00
7-10 Days
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Power Meter Consoles

Our most popular power meter consoles are included here for convenience. The PM100D digital power meter console features a back-lit LED screen and includes a 1 GB external SD memory card. The PM400 touch screen power meter console can perform the same functions as the PM100D with added features that include storing past power measurements in its 4 GB internal memory, inputs for external temperature and humidity sensors, programmable GPIO ports, and a capacitive touchscreen display that allows the unit to be operated with multi-touch gestures. Additionally, the PM400 allows optical power measurement data, temperature logs, spectral correction curves, and attenuation correction data can be saved by the user and transfered between the console and an external device for further analysis. These functions are particularly useful for tracking the consistency of the power at the sample plane over time. For more information, click on the part number in the table below to view the complete presentation for each power meter console.

Alternatively, the NS170C sensor is compatible with the PM5020 and the previous-generation PM200 and PM320E consoles. It can also be used with the PM100 seriesPM100USB, and PM103 series interfaces.

Item # PM100A PM100D PM400
Console Image
(Click the Image to Enlarge)
PM100A PM100D PM400 Power Meter Console
Display Mechanical Needle and
LCD Display with Digital Readout
320 x 240 Pixel Backlit
Graphical LCD Display
Projected Capacitive Touchscreen
with Color Display
Output Analog Needle or Digital Numeric Readout Numerical, Bar Graph, Statistics,
Simulated Analog Needle
Numerical with Bar Graph,
Trend Graph (Power or Energy
and Temperature),
Statistics, Simulated Analog Needle
Calibration Functions Wavelength Correctiona Wavelength Correctiona Wavelength Correctiona;
Also Accepts User-Input
Source Spectra and
Attenuation Correction Data
Data Storage and Transfer USB 2.0 Interface 1 GB External SD Memory Card,
USB 2.0 Interface
4 GB Internal Memory
Mini B USB 2.0 Interface
Dimensions 7.24" x 4.29" x 1.61"
(184 mm x 109 mm x 41 mm)
7.09" x 4.13" x 1.50"
(180 mm x 105 mm x 38 mm)
5.35" x 3.78" x 1.16"
(136.0 mm x 96.0 mm x 29.5 mm)
Display Dimensions 1.9" x 0.5" (48.2 mm x 13.2 mm)
Digital Display and
3.54" x 1.65" (90.0 mm x 42.0 mm) Analog Display
3.17" x 2.36"
(81.4 mm x 61.0 mm)
3.7" x 2.1"
(95 mm x 54 mm)
  • Sensor Dependent
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PM100A Support Documentation
PM100ACompact Power Meter Console, Mechanical Analog & Graphical LC Display
$1,114.91
Today
PM100D Support Documentation
PM100DCompact Power and Energy Meter Console, Digital 4" LCD
$1,270.39
Today
PM400 Support Documentation
PM400Projected Capacitive Touchscreen Optical Power and Energy Meter Console
$1,583.35
Today
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Recalibration Service for Microscope Slide Peak Power Sensor

Calibration Service
Item #
Compatible Microscope
Slide Power Sensor
CAL-NS NS170C

Thorlabs offers a recalibration service for our microsope slide peak Power sensor. To ensure accurate measurements, we recommend recalibrating the sensor annually. Recalibration of a single-channel power and/or energy meter console or interface is included with the recalibration of a sensor at no additional cost. If you wish to calibrate one or more sensors with a dual-channel console, each sensor and console calibration service will need to be purchased individually.

Refer to the table to the right for the appropriate calibration service Item # that corresponds to your microscope slide power sensor.

Requesting a Calibration
Thorlabs provides two options for requesting a calibration:

  1. Complete the Returns Material Authorization (RMA) form. When completing the RMA form, please enter your name, contact information, the Part #, and the Serial # of the item being returned for calibration; in the Reason for Return field, select "I would like an item to be calibrated." All other fields are optional. Once the form has been submitted, a member of our RMA team will reach out to provide an RMA Number, return instructions, and to verify billing and payment information.
  2. Select the appropriate sensor calibration Item # below, enter the Part # and Serial # of the sensor that requires recalibration, and then Add to Cart. If you would like a console calibrated with your sensor, repeat this process for Item # CAL-PM1 or CAL-PM2 below, entering the console Item # and Serial #. A member of our RMA team will reach out to coordinate the return of the item(s) for calibration. Note that each console calibration Item # represents the cost of calibrating a console alone; if requesting a single-channel console calibration with a sensor calibration, the appropriate discount will be applied when your request is processed. Should you have other items in your cart, note that the calibration request will be split off from your order for RMA processing.

Please Note: To ensure your item being returned for calibration is routed appropriately once it arrives at our facility, please do not ship it prior to being provided an RMA Number and return instructions by a member of our team.

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CAL-NS Support Documentation
CAL-NSNEW!Recalibration Service for Second-Order Nonlinear Crystal with Silicon Photodiode Sensor
Part Number:  Serial Number:
Request
Lead Time
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Recalibration of Power & Energy Meter Electronics

Calibration Service Item # Compatible Consoles & Interfaces
Single-Channel
CAL-PM1 PM100D, PM100A, PM400, PM100USB,
PM101 Series, PM102 Series, PM103 Series
Dual-Channel
CAL-PM2 PM5020, Previous-Generation PM320E

These recalibration services are for the power and/or energy meter electronics of our consoles and interfaces. To ensure accurate measurements, we recommend recalibrating annually. Recalibration of a single-channel console or interface is included with these sensor recalibration services at no additional cost. If you wish to calibrate one or more sensors with a dual-channel console, each sensor and console calibration service will need to be purchased individually. For more details on these recalibration services, please click the Documents () icons below. 

The table to the upper right lists the power and/or energy meter consoles and interfaces that can be calibrated using the CAL-PM1 and CAL-PM2 recalibration services.

Requesting a Calibration
Thorlabs provides two options for requesting a calibration:

  1. Complete the Returns Material Authorization (RMA) form. When completing the RMA form, please enter your name, contact information, the Part #, and the Serial # of each item being returned for calibration; in the Reason for Return field, select "I would like an item to be calibrated." All other fields are optional. Once the form has been submitted, a member of our RMA team will reach out to provide an RMA Number, return instructions, and to verify billing and payment information.
  2. Select the appropriate Item # below, enter the Part # and Serial # of the item that requires recalibration, and then Add to Cart. If you would like to calibrate one or more sensors with your console, repeat this process for the appropriate sensor recalibration service above, entering the console Item # and Serial #. A member of our RMA team will reach out to coordinate return of the item(s) for calibration. Note that each console calibration Item # represents the cost of calibrating a console alone; if requesting a single-channel console calibration with a sensor calibration, the appropriate discount will be applied when your request is processed. Should you have other items in your cart, note that the calibration request will be split off from your order for RMA processing.

Please Note: To ensure your item being returned for calibration is routed appropriately once it arrives at our facility, please do not ship it prior to being provided an RMA Number and return instructions by a member of our team.

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
CAL-PM1 Support Documentation
CAL-PM1Recalibration of Single-Channel Power and/or Energy Meter Electronics
Part Number:  Serial Number:
$78.80
Lead Time
CAL-PM2 Support Documentation
CAL-PM2Recalibration of Dual-Channel Power and Energy Meter Electronics
Part Number:  Serial Number:
$210.12
Lead Time