Features

• For Measurements Independent of Beam Shape and Entrance Angle
• Integrating Sphere Design Acts as a Diffuser with Minimal Power Loss
• Ø5 mm, Ø7 mm, Ø12 mm, or Ø22 mm Input Aperture
• Individually Calibrated with NIST- or PTB-Traceable Certificate of Calibration
• Over-Temperature Alert Sensor
• Spheres with Apertures ≤Ø12 mm Include a Removable S120-FC Fiber Adapter (FC/PC and FC/APC) 
• Additional Fiber Adapters Available Separately (See Below)
• C-Series Connector Design for Quick Sensor Connection
• Recalibration Services Available

Integrating spheres are designed to provide precise optical power measurements independent of beam shape, entrance angle, and polarization. These photodiode sensors have a faster response time than thermal sensor heads while also offering a high damage threshold. These integrating spheres feature enhanced shielding to avoid electromagnetic interference and an over-temperature alert sensor to warn against damage and measurement errors due to overheating of the sensor.

Our integrating spheres are designed for wavelength ranges from the visible through the NIR. Sensor heads for use between 350 nm and 2500 nm use a single Ø1" or Ø2" sphere made from Zenith^® PTFE and feature a black housing to minimize reflected light around the entrance aperture. These sensors use either a silicon photodiode for detection in the 350 nm - 1100 nm range or an InGaAs photodiode for detection in the 800 nm - 1700 nm, 900 nm - 1650 nm, or 1200 nm - 2500 nm wavelength range. The integrating sphere housing has separate or combined (see Specs tab) 8-32 and M4 taps that can be used to mount the sensor on a standard Ø1/2" post (not included).

Click to Enlarge
Figure 1.1  A baffle on the S142CL and S145CL spheres blocks light from directly hitting the detector.

The S180C integrating sphere for 2.9 µm - 5.5 µm uses two connected, gold-plated Ø20 mm spheres, with an entrance port in the first sphere and a port for the MCT (HgCdTe) detector located in the second sphere. Compared to single-sphere designs, the two-sphere configuration improves device sensitivity by minimizing the internal sphere surface area while still effectively shielding the detector from direct illumination. This design reduces the effect of input angle, divergence, and beam shape on the measurement result by effectively shielding the photodiode without the use of a baffle or other shielding mechanism. The integrating sphere housing has one universal 8-32 and M4 tap that can be used to mount the sensor on a standard Ø1/2" post (not included).

The integrating spheres with Ø5 mm, Ø7 mm, or Ø12 mm apertures include an adapter with external SM1 (1.035"-40) threads as well as an S120-FC fiber adapter for compatibility with FC/PC- and FC/APC-terminated patch cables, supporting easy integration with both free-space and fiber-coupled setups, as shown in Figure 4.1 in the Mounting Options tab. Additional fiber adapters for other connector types are available separately below. The externally SM1-threaded adapter can be removed using a size 1 screwdriver to place components closer to the window. 

The S142CL and S145CL integrating spheres feature a large Ø22 mm input aperture and a baffle within the sphere which prevents direct illumination of the photodiode. The large aperture and baffle enable measurements of large and divergent beams, such as those emitted from LED and VCSEL light sources. The input face of the detectors have four 4-40 threads for mounting 30 mm cage system components. Additionally, insertion of a second or third port in the sensor head is possible on request, please contact Tech Support for details.

Compatibility and Calibration
These integrating spheres have C-Series connectors for compatibility with Thorlabs' line of power meter consoles; compatible consoles are outlined in the Compatible Power Meter Consoles box and details are provided on the Console Selection tab. Each sensor head is individually calibrated and is shipped with NIST- or PTB-traceable calibration data. The included data will match the calibration certification of the photodiode used to test the individual sensor. The calibration data and sensor identification information is stored in the red connector and read out automatically when the sensor is connected to a compatible Thorlabs power meter console.

Thorlabs also offers power sensor heads in a wide range of other formats as well as complete power meters that combine a sensor head and power meter electronics in a compact package. Our complete line of sensor heads, power meter consoles, and complete power meters is available here.

Recalibration Services
Thorlabs offers recalibration services for our integrating sphere power sensors. We recommend recalibrating your Thorlabs sensor and console as a pair; however, each may be recalibrated individually. All of the sensors on this page come with a manufacturer calibration by default, but we also offer an ISO 17025 accredited calibration for some items. For more information on calibration options, please see the Recalibration tab or the calibration sections at the bottom of this page.

Item #	S140C	S142C	S142CL	S144C	S145C	S145CL	S146C	S148C	S180C
Technical Specs
Detector Type	Si Photodiode		Si Photodiode w/Baffle	InGaAs Photodiode		InGaAs Photodiode w/Baffle	InGaAs Photodiode	Extended InGaAs Photodiode	MCT (HgCdTe) Photodiode
Wavelength Range	350 nm - 1100 nm		400 nm - 1100 nm	800 nm - 1700 nm			900 nm - 1650 nm	1200 nm - 2500 nm	2.9 µm - 5.5 µm
Optical Power Range	1 µW - 500 mW	1 µW - 5 W	10 µW - 5 W	1 µW - 500 mW	1 µW - 3 W	10 µW - 3 W	10 µW - 20 W	1 µW - 1 W	1 µW - 3 W
Max Average Power Density	1 kW/cm2	2 kW/cm2		1 kW/cm2	2 kW/cm2			1 kW/cm2
Max Pulse Energy Density	1 J/cm2	7 J/cm2		1 J/cm2	7 J/cm2			1 J/cm2
Linearity	±0.5%
Resolutiona	1 nW		10 nW	1 nW		10 nW		1 nW	10 nW
Measurement Uncertaintyb,c	±3% (440 - 980 nm) ±5% (350 - 439 nm) ±7% (981 - 1100 nm)		±3% (440 - 980 nm) ±5% (400 - 439 nm) ±7% (981 - 1100 nm)	±5%
Responsivityd (Click for Plot)	Raw Data	Raw Data	Raw Data	Raw Data	Raw Data	Raw Data	Raw Data	Raw Data	Raw Data
General Information
Typical Application	Low- and Mid-Power Lasers / Fiber Lasers / LEDs								Low- and Mid-Power Lasers / Fiber Lasers
Laser Types	Diode, He-Cd, ArIo, KrIo, Dye, Ti-Sapphire		Diode, He-Cd, ArIo, KrIo, Dye, Ti-Sapphire, VCSEL	Diode, He-Cd, ArIo, KrIo, Dye, Ti-Sapphire		Diode, He-Cd, ArIo, KrIo, Dye, Ti-Sapphire, VCSEL	Diode, He-Cd, ArIo, KrIo, Dye, Ti-Sapphire		QCL, ICL, HeNe, CO, Er:YAG, Co2+:ZnS
Integrating Sphere Material (Size)	Zenith® PTFE (Ø1")	Zenith® PTFE (Ø2")		Zenith® PTFE (Ø1")	Zenith® PTFE (Ø2")			Zenith® PTFE  (Ø1")	Gold Plating (Two Ø20 mm Spheres)
Cooling	Convection
Head Temperature Measurement	NTC Thermistor, 4.7 kΩ
Compatible Consolese	PM100A, PM100D2, PM100D3, PM400, and PM5020
Compatibile Interfacese	PM101, PM101A, PM101R, PM101U, PM103, PM103A, PM103E, PM103U, and PM100USB
Response Time	<1 µs
Mechanical Specs
Housing Dimensions	Ø45 mm x 30.5 mm	70 mm x 74 mm x 70 mm		Ø45 mm x 30.5 mm	70 mm x 74 mm x 70 mm			Ø45 mm x 30.5 mm	59.0 mm x 50.0 mm x 28.5 mm
Active Sensor Area	3.6 mm x 3.6 mm				Ø2 mm	Ø3 mm	Ø1 mm	Ø1 mm	1 mm x 1 mm
Sensor Aperture	Ø5 mm	Ø12 mm	Ø22 mm	Ø5 mm	Ø12 mm	Ø22 mm	Ø12 mm	Ø5 mm	Ø7 mm
Cable Length	1.5 m
Connector	Male 9-Pin D-Sub
Weight	0.2 kg	0.6 kg		0.2 kg	0.6 kg			0.2 kg	0.25 kg
Mounting and Accessories
Mounting Thread	Separate 8-32 and M4 Taps, Posts Not Included		Universal 8-32 / M4 Thread, Post Not Included	Separate 8-32 and M4 Taps, Posts Not Included		Universal 8-32 / M4 Thread, Post Not Included	Separate 8-32 and M4 Taps, Posts Not Included		Universal 8-32 / M4 Tap, Post Not Included
Aperture Thread	Included Adapter with SM1 (1.035"-40) External Thread		None	Included Adapter with SM1 (1.035"-40) External Thread		None	Included Adapter with SM1 (1.035"-40) External Thread
Fiber Adapters (Optional)	FC (Included), SMA, ST®f, LC, SC, Ø2.5 mm Ferrule, Bare Fiber		None	FC (Included), SMA, ST®f, LC, SC, Ø2.5 mm Ferrule, Bare Fiber		None	FC (Included), SMA, ST®f, LC, SC, Ø2.5 mm Ferrule, Bare Fiber

• Measured with the previous-generation PM100D console in the low bandwidth setting.
• Parallel Beam Diameter > 1 mm
• Uncertainties for S142CL and S145CL are valid at a temperature of 24 °C ± 2 °C.
• All sensor responsivities shown in these plots were calibrated to a NIST-traceable source with measurements taken in 5 nm intervals except for the S180C. See the S180C responsivity graph to see the NIST-traceable reference points.
• The sensors are compatible with all currently available photodiode power meters. For compatibility with legacy products, ask Tech Support.
• ST^® is a registered trademark of Lucent Technologies, Inc.

Integrating Sphere Photodiode Sensor Mounting Options

Click to Expand
Figure 4.2  S140C and S140-BFA Fiber Adapter

Click to Expand
Figure 4.1  S140C and S120-FC Fiber Adapter

Thorlabs' Integrating Sphere Photodiode Sensors provide a low-loss cavity for diverging, non-uniform, or off-axis beam measurements. These integrating spheres are ideal for all fiber-based applications due to the beam divergence at the end of the fiber.

Shown in Figure 4.1 is an S140C Integrating Sphere with an S120-FC Fiber Adapter and shown in Figure 4.2 is an S140C with an S140-BFA Bare Fiber Adapter. The bare fiber adapter features a mounting clamp and light shield to decrease interference from ambient light.

Thorlabs offers a wide selection of power and energy meter consoles and interfaces for operating our power and energy sensors. Key specifications of all of our power meter consoles and interfaces are presented in this tab to help you decide which device is best for your application. We also offer self-contained wireless power meters and compact USB power meters.

When used with our C-series sensors, Thorlabs' power meter consoles and interfaces recognize the type of connected sensor and measure the current or voltage as appropriate. Our C-series sensors have responsivity calibration data stored in their connectors. The console will read out the responsivity value for the user-entered wavelength and calculate a power or energy reading.

• Photodiode sensors deliver a current that depends on the input optical power and the wavelength. The current is fed into a transimpedance amplifier, which outputs a voltage proportional to the input current. The photodiode's responsivity is wavelength dependent, so the correct wavelength must be entered into the console for an accurate power reading. The console reads out the responsivity for this wavelength from the connected sensor and calculates the optical power from the measured photocurrent.
• Thermal sensors deliver a voltage proportional to the input optical power. Based on the measured sensor output voltage and the sensor's responsivity, the console will calculate the incident optical power.
• Thermal position and energy sensors incorporate four thermopiles arranged as quadrants of a square. By comparing the voltage output from each quadrant, the unit calculates the beam's position.
• Energy sensors are based on the pyroelectric effect. They deliver a voltage peak proportional to the pulse energy. If an energy sensor is recognized, the console will use a peak voltage detector, and the pulse energy will be calculated from the sensor's responsivity.

The consoles and interfaces are also capable of providing a readout of the current or voltage delivered by the sensor. Select models also feature an analog output.

Consoles

Item #	PM100A	PM100D2	PM100D3	PM400	PM5020
(Click Photo to Enlarge)
Sensor Compatibility (Sensors Not Included)
Photodiode Power
Thermal Power
Thermal Position & Power	-	-
Pyroelectric Energy	-			a
Key Features
Housing Dimensions (H x W x D)	7.24" x 4.29" x 1.61" (184 mm x 109 mm x 41 mm)	6.42" x 3.87" x 1.38" (163.0 mm x 98.4 mm x 35.0 mm)		5.35" x 3.78" x 1.16" (136.0 mm x 96.0 mm x 29.5 mm)	9.97" x 4.35" x 11.56" (253.2 mm x 110.6 mm x 293.6 mm)
Channels	1				2
External Temperature Sensor Input (Sensor Not Included)	-	-	Readout and Record Temperature Over Time
External Humidity Sensor Input (Sensor Not Included)	-	-	Readout and Record Humidity Over Time
Analog Outputb	Amplified Input Signal, SMA, 0 to 2 V, Up to 100 kHz	Amplified Input Signal or 12-bit DAC Corrected Input Signal, SMA, 0 to 2.5 V, Up to 100 kHz	Amplified Input Signal, 12-bit DAC Corrected Input Signal, or 14-bit DAC Corrected X-Y Position Signal, SMA, 0 to 2.5 V (Power); -2.0 to 2.0 V (Position), Up to 100 kHz	Amplified Input Signal or DAC Corrected Input Signal, 2p Audio 3.5 mm (Adapter to BNC included), 0 to 2 V, Up to 100 kHz	Amplified Input Signal or DAC Corrected Input Signal, 2 x BNC, -2.5 to 10 V, Up to 250 kHz. Programmable AOc, 4 x BNC, -5 to 10 V, Up to 1 kHz
Input/Output Ports	-		26-Pin AUX Connector With 4 GPIO, AN OUT for Power (Analog Input Signal and 12-bit DAC) and Position Sensor (14-bit DAC), I2C, UART, and Analog and Digital Supply Voltages	14-Pin AUX Connector With 4 GPIO, Programmable, 2 x 10 bit ADC for External Temperature, Relative Humidity Sensor, +3.3 V, ±2.5 V (100 mA Max)	10-Pin PCB Connector, 4 Configurable Digital I/O Channels, 1 Trigger In/Out, I2C (LVTTL / TTL)
Shutter Control	-	-	-	-	Support for SH05R(/M) or SH1(/M) Optical Shutter with Interlock Input
Fan Control	-	-	-	-
Source Spectral Correction	-
Attenuation Correction	-
External Trigger Input	-	-		-
Display
Type	Mechanical Needle and LCD Display with Digital Readout	3.5" Full Color Touchscreen Display, 640 x 480 Pixels		4.3" Protected Capacitive Touchscreen with Color Display, 400 x 272 Pixels	5" IPS Touchscreen LCD Display, 854 x 480 Pixels
Dimensions	Digital: 1.9" x 0.5" (48.2 mm x 13.2 mm) Analog: 3.54" x 1.65" (90.0 mm x 42.0 mm)	2.80" x 2.10" (71.0 mm x 53.3 mm)		3.7" x 2.1" (95 mm x 54 mm)	4.32" x 2.43" (109.7 mm x 61.6 mm)
Refresh Rate	20 Hz	50 Hz		10 Hz (Numerical) 25 Hz (Analog Simulation)	25 Hz
Measurement Viewsd
Numerical
Mechanical Analog Needle		-	-	-	-
Simulated Analog Needle	-
Bar Graph	-
Trend Graph	-
Statistics
Pass/Fail	-	-		-	-
Scope	-	-		-
Memory
Type	-	eMMC Flash		NAND Flash	SD Card
Size	-	8 GB		4 GB	8 GB
Power
Battery	LiPo 3.7 V 2300 mAh	LiPo 3.7 V 2300 mAh		LiPo 3.7 V 2300 mAh	-
External	5 VDC via USB or Included AC Adapter	5 VDC via USB-C Connector		5 VDC via USB Mini B Connector	Line Voltage: 100 - 240 V

• As the PM400 console can only support repetition rates of up to 3 kHz, it should not be used with the ES408C sensor, which detects repetition rates up to 10 kHz.
• The analog output bandwidth is dependent on the sensor and settings.
• Selectable from the following options: CH1, CH2, CH1 - CH2, CH1/CH2, Position X, Position Y. Programmable gain and offset.
• These are the measurement views built into the unit.

Interfaces

Item #	PM101	PM102	PM103	PM101A	PM102A	PM103A
(Click Photo to Enlarge)
Operation Protocol	USB, RS232, UART, and Analog			USB and Analog SMA
Sensor Compatibility
Photodiode		-			-
Thermal Power			-			-
Thermal Position & Power	-		-	-		-
Pyroelectric	-	-		-	-

Key Features
C-Series Sensor DE-9 Connector
USB Connector	Lockable			Lockable
USB Max Measurement Speed	1000 S/s	1000 S/s	100 000 S/s	1000 S/s	1000 S/s	100 000 S/s
Serial DE-9 Connector	-			-
DE-9 Max Measurement Speed	-			-
SMA Connector(s)	-			1 Analog Power Output	3 Ports: Power, X-Position, and Y-Position	3 Ports: AO1, AO2, and Digital I/O (Configurable as External Trigger Input)
DA-15 Universal Connector with 2 Auxiliary I/O Ports			GPIO Ports Also Configurable as Trigger Input (Pin 2) or for Pass/Fail Analysis (Pin 3)	-
DA-15 Max Measurement Speed	200 S/s	200 S/s	100 000 S/s	-
Ethernet (RJ45) Connector	-	-	-	-
Ethernet Max Measurement Speed	-	-	-	-
Phoenix DMC 0,5/7 Connector	-	-	-	-
DMC 0,5/7 Max Measurement Speed	-	-	-	-
External Temperature Sensor Input (Sensor Not Included)	NTC Thermistor			-
Display
Type	No Built-In Display; Controlled via GUI for PC
Measurement Viewsc
Numerical	Requires PC
Simulated Analog Needle	Requires PC
Bar Graph	Requires PC
Trend Graph	Requires PC
Histogram	Requires PC
Statistics	Requires PC
Memory
Type	Internal Non-Volatile Memoryfor All Settings
Power
External	5 VDC via USB or 5 to 36 VDC via DA-15 Pins 1 and 9			5 VDC via USB

Item #	PM103E	PM101R	PM101U	PM102U	PM103U	PM100USB
(Click Photo to Enlarge)
Operation Protocol	Ethernet, RS232, and Analog	USB and RS232	USB Operation			USB
Sensor Compatibility
Photodiode				-
Thermal Power					-
Thermal Position & Power		-	-		-	-
Pyroelectric		-	-	-		a

Key Features
C-Series Sensor DE-9 Connector
USB Connector	-	Lockable	Lockable			Not Lockable
USB Max Measurement Speed	-	1000 S/s	1000 S/s	1000 S/s	100 000 S/s	300 S/s
Serial DE-9 Connector	-		-			-
DE-9 Max Measurement Speed	-	200 S/s	-			-
SMA Connector(s)	-	-	-			-
DA-15 Universal Connector with 2 Auxiliary I/O Ports	-	-	-			-
DA-15 Max Measurement Speed	-	-	-			-
Ethernet (RJ45) Connector		-	-			-
Ethernet Max Measurement Speed	100 000 S/s	-	-			-
Phoenix DMC 0,5/7 Connector		-	-			-
DMC 0,5/7 Max Measurement Speed	100 000 S/s	-	-			-
External Temperature Sensor Input (Sensor Not Included)	NTC Thermistor	-	-			-
Display
Type	No Built-In Display; Controlled via GUI for PC
Measurement Viewsc
Numerical	Requires PC
Simulated Analog Needle	Requires PC
Bar Graph	Requires PC
Trend Graph	Requires PC
Histogram	Requires PC
Statistics	Requires PC
Memory
Type	Internal Non-Volatile Memory for All Settings					-
Power
External	Power over Ethernetd and 5 to 36 VDC via DMC 0,5/7 pin 1 and 2	5 VDC via USB	5 VDC via USB			5 VDC via USB

• As the PM100USB interface can only support repetition rates of up to 3 kHz, it should not be used with the ES408C sensor, which detects repetition rates up to 10 kHz.
• Dependent on PC Settings
• These power meter interfaces do not have a built-in monitor, so all data must be displayed through a PC running the Optical Power Monitor Software.
• 48 V is the nominal voltage over the network, but can range from 36 V - 57 V.

Insights into Best Lab Practices

Scroll down to read about things to consider when building integrating spheres into setups and analyzing data results.

• Ultraviolet and Blue Fluorescence Emitted by Integrating Spheres
• Sample Substitution Errors

Click here for more insights into lab practices and equipment.

Ultraviolet and Blue Fluorescence Emitted by Integrating Spheres

Click to Enlarge
Figure 182A  Typical yields at each wavelength are around four orders of magnitude lower than the excitation wavelength. [4]

The spectral fluorescence yield relates the intensity of the fluorescence emitted within the integrating sphere with the intensity of the excitation wavelength. The yield is calculated by dividing the wavelength-dependent, total fluorescence excited over the entire interior surface of the sphere by the intensity of the light excitation.

Data were kindly provided by Dr. Ping-Shine Shaw, Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.

A material of choice for coating the light-diffusing cavities of integrating spheres is polytetrafluoroethylene (PTFE). This material, which is white in appearance, is favored for reasons including its high, flat reflectance over a wide range of wavelengths (see the Specs tab for details) and chemical inertness.

However, it should be noted that integrating spheres coated with both PTFE and barium sulfate, which is an alternative coating with lower reflectance, emit low levels of ultraviolet (UV) and blue fluorescence when irradiated by UV light. [1-3]

Hydrocarbons in the PTFE Fluoresce
It is not the PTFE that fluoresces. The sources of the UV and blue fluorescence are hydrocarbons in the PTFE. Low levels of hydrocarbon impurities are present in the raw coating material, and pollution sources deposit additional hydrocarbon contaminants in the PTFE material of the integrating sphere during its use and storage. [1]

Fluorescence Wavelength Bands and Strength
Researchers at the National Institute of Standards and Technology (NIST) have investigated the fluorescence excited by illuminating PTFE-coated integrating spheres. The total fluorescence output by the integrating sphere was measured with respect to fluorescence wavelength and excitation wavelength. The maximum fluorescence was approximately four orders of magnitude lower than the intensity of the exciting radiation.

The UV and blue fluorescence from PTFE is primarily excited by incident wavelengths in a 200 nm to 300 nm absorption band. The fluorescence is emitted in the 250 nm to 400 nm wavelength range, as shown by Figure 182A. These data indicate that increasing the excitation wavelength decreases the fluorescence emitted at lower wavelengths and changes the shape of the fluorescence spectrum.

As the levels of hydrocarbon contaminants in the PFTE increase, fluorescence increases. A related effect is a decrease of the light output by the integrating sphere over the absorption band wavelengths, due to more light from this spectral region being absorbed. [1, 3]

Impact on Applications
The UV and blue fluorescence from the PTFE has negligible effect on many applications, since the intensity of the fluorescence is low and primarily excited by incident wavelengths <300 nm. Applications sensitive to this fluorescence include long-term measurements of UV radiation throughput, UV source calibration, establishing UV reflectance standards, and performing some UV remote sensing tasks. [1]

Minimizing Fluorescence Effects
Minimizing and stabilizing the fluorescence levels requires isolating the integrating sphere from all sources of hydrocarbons, including gasoline- and diesel-burning engine exhaust and organic solvents, such as naphthalene and toluene. It should be noted that, while hydrocarbon contamination can be minimized and reduced, it cannot be eliminated. [1]

Since the history of each integrating sphere's exposure to hydrocarbon contaminants is unique, it is not possible to predict the response of a particular sphere to incident radiation. When an application is negatively impacted by the fluorescence, calibration of the integrating sphere is recommended. A calibration procedure described in [4] requires a light source with a well-known spectrum that extends across the wavelength region of interest, such as a deuterium lamp or synchrotron radiation, a monochromator, a detector, and the integrating sphere.

References
[1] Ping-Shine Shaw, Zhigang Li, Uwe Arp, and Keith R. Lykke, "Ultraviolet characterization of integrating spheres," Appl.Opt. 46, 5119-5128 (2007).
[2] Jan Valenta, "Photoluminescence of the integrating sphere walls, its influence on the absolute quantum yield measurements and correction methods," AIP Advances 8, 102123 (2018).
[3] Robert D. Saunders and William R. Ott, "Spectral irradiance measurements: effect of UV-produced fluorescence in integrating spheres," Appl. Opt. 15, 827-828 (1976).
[4] Ping-Shine Shaw, Uwe Arp, and Keith R. Lykke, "Measurement of the ultraviolet-induced fluorescence yield from integrating spheres," Metrologia 46, S191 - S196 (2009).

Date of Last Edit: Dec. 4, 2019

Sample Substitution Errors

Click to Enlarge
Figure 182B  Measuring diffuse sample transmittance and reflectance as shown here can result in a distorted sample spectrum due to sample substitution error. The problem is that the reflectivity over the sample area is different during the reference and sample measurements.

Click to Enlarge
Figure 182C  This configuration is not susceptible to sample substitution error, since the interior of the sphere is the same for reference and sample measurements. During the reference measurement the light travels along (R), and no light is incident along (S). The opposite is true when a sample measurement is made.

Absolute transmittance and absolute diffuse reflectance spectra of optical samples can be found using integrating spheres. These spectra are found by performing spectral measurements of both the sample of interest and a reference.

Measurement of a reference is needed since this provides the spectrum of the illuminating light source. Obtaining the reference scan allows the spectrum of the light source to be subtracted from the sample measurement.

The light source reference measurement is made with no sample in place for transmittance data and with a highly reflective white standard reference sample in place for reflectance measurements.

Sample substitution errors incurred while acquiring the sample and reference measurement sets can negatively effect the accuracy of the corrected sample spectrum, unless the chosen experimental technique is immune to these errors.

Conditions Leading to Sample Substitution Errors
An integrating sphere's optical performance depends on the reflectance at each point on its entire inner surface. Often, a section of the sphere's inner wall is replaced by the sample when its transmittance and diffuse reflectance spectra are measured (Figure 182B). However, modifying a section of the inner wall alters the performance of the integrating sphere.

Sample substitution errors are a concern when the measurement procedure involves physically changing one sample installed within the sphere for another. For example, when measuring diffuse reflectance (Figure 182B, bottom), a first measurement might be made with the standard reference sample mounted inside the sphere. Next, this sample would be removed and replaced by the sample of interest, and a second measurement would be acquired. Both data sets would then be used to calculate the corrected absolute diffuse reflectance spectrum of the sample.

This procedure would result in a distorted absolute sample spectrum. Since the sample of interest and the standard reference have different absorption and scattering properties, exchanging them alters the reflectivity of the integrating sphere over the samples' surface areas. Due to the average reflectivity of the integrating sphere being different for the two measurements, they are not perfectly compatible.

Solution Option: Install Sample and Reference Together
One experimental technique that avoids sample substitution errors acquires measurement data when both sample and reference are installed inside the integrating sphere at the same time. This approach requires an integrating sphere large enough to accomodate the two, as additional ports.

The light source is located external to the integrating sphere, and measurements of the sample and standard reference are acquired sequentially. The specular reflection from the sample, or the transmitted beam, is often routed out of the sphere, so that only the diffuse light is detected. Since the inner surface of the sphere is identical for both measurements, sample substitution errors are not a concern.

Alternate Solution Option: Make Measurements from Sample and Reference Ports
If it is not possible to install both sample and standard references in the integrating sphere at the same time, it is necessary to exchange the installed sample. If this must be done, sample substitution errors can be removed by following the procedure detailed in [1].

This procedure requires a total of four measurements. When the standard sample is installed, measurements are made from two different ports. One has a field of view that includes the sample and the other does not. The sample of interest is then subsituted in and the measurements are repeated. Performing the calculations described in [1] using these measurements removes the sample substitution errors.

References
[1] Luka Vidovic and Boris Majaron, "Elimination of single-beam substitution error in diffuse reflectance measurements using an integrating sphere," J. Biomed.Opt. 19, 027006 (2014).

Date of Last Edit: Dec. 4, 2019

Click to Enlarge
Figure 113A  The PM160 wireless power meter, shown here with an iPad mini (not included), can be remotely operated using Apple mobile devices.

This tab outlines the full selection of Thorlabs' power and energy sensors. Refer to Table 113B for power meter console and interface compatibility information.

In addition to the power and energy sensors listed below, Thorlabs also offers all-in-one, wireless, handheld power meters and compact USB power meter interfaces that contain either a photodiode or a thermal sensor, as well as power meter bundles that include a console, sensor head, and post mounting accessories.

Thorlabs offers four types of sensors:

• Photodiode Sensors: These sensors are designed for power measurements of monochromatic or near-monochromatic sources, as they have a wavelength dependent responsivity. These sensors deliver a current that depends on the input optical power and the wavelength. The current is fed into a transimpedance amplifier, which outputs a voltage proportional to the input current.
• Thermal Sensors: Constructed from material with a relatively flat response function across a wide range of wavelengths, these thermopile sensors are suitable for power measurements of broadband sources such as LEDs and SLDs. Thermal sensors deliver a voltage proportional to the input optical power.
• Thermal Position & Power Sensors: These sensors incorporate four thermopiles arranged as quadrants of a square. By comparing the voltage output from each quadrant, the unit calculates the beam's position.
• Pyroelectric Energy Sensors: Our pyroelectric sensors produce an output voltage through the pyroelectric effect and are suitable for measuring pulsed sources, with a repetition rate limited by the time constant of the detector. These sensors will output a peak voltage proportional to the incident pulse energy.

Table 113B  Console Compatibility
Console Item #	PM100A	PM100D2	PM100D3	PM400	PM5020	PM101 Series	PM102 Series	PM103 Series	PM100USB
Photodiode Power							-
Thermal Power								-
Thermal Position	-	-				-		-	-
Pyroelectric Energy	-			a		-	-		a

• As the PM400 console and the PM100USB interface can only support repetition rates of up to 3 kHz, they should not be used with the ES408C sensor, which detects repetition rates up to 10 kHz.

Power and Energy Sensor Selection Guide

There are two options for comparing the specifications of our Power and Energy Sensors. Tables 113C, 113D, 113E, and 113F sort our sensors by type (e.g., photodiode, thermal, or pyroelectric) and provide key specifications.

Alternatively, the selection guide Figures 113G and 113H arrange our entire selection of photodiode and thermal power sensors by wavelength (Figure 113G) or optical power range (Figure 113H). Each box contains the item # and specified range of the sensor. These graphs allow for easy identification of the sensor heads available for a specific wavelength or power range.

Sensor Type	Applications	Item #	Wavelength	Energy or Power Range	Detector Type	Aperture	Response Time
Standard Sensors	General Purpose Power Measurements	S120VC	200 - 1100 nm	50 nW - 50 mW (200 - 450 nm) 50 nW - 20 mW (450 - 1100 nm)	Si	Ø9.5 mm	<1 µsa
		S120C	400 - 1100 nm	50 nW - 50 mW		Ø9.5 mm
		S121C	400 - 1100 nm	500 nW - 500 mW		Ø9.5 mm
		S122C	700 - 1800 nm	50 nW - 40 mW	Ge	Ø9.5 mm
Slim Sensors	Power Measurements in Tight Spaces such as 30 mm Cage Systems	S130VC	200 - 450 nm	500 pW - 0.5 mW (Up to 50 mW with Filter)	Si Slim	Ø9.5 mm
			450 - 1100 nm	500 pW - 0.2 mW (Up to 20 mW with Filter)
		S130C	400 - 1100 nm	500 pW - 5 mW (Up to 500 mW with Filter)		Ø9.5 mm
		S132C	700 - 1800 nm	5 nW - 5 mW (Up to 500 mW with Filter)	Ge Slim	Ø9.5 mm
Compact Slim Sensor	Power Measurements in Tight Spaces such as 16 mm Cage Systems	S116C	400 - 1100 nm	20 nW - 50 mW	Si Compact Slim	Ø6 mm
Microscope Slide Sensor	Measure Power at the Sample Plane of a Microscope	S170C	350 - 1100 nm	10 nW - 150 mW	Si Large Area	18 mm x 18 mm
	Measure Relative Peak Power at the Sample Plane of a Microscope	NS170C	780 - 1300 nm	0.5 W - 350 mWb	Si Large Area with Second-Order Nonlinear Crystal	Ø4.5 mm
Integrating Sphere Sensors	Power Measurements for High Powers and Divergent Beams	S140C	350 - 1100 nm	1 µW - 500 mW	Si Integrating	Ø5 mm
		S142C	350 - 1100 nm	5 µW - 5 W		Ø12 mm
		S142CL	400 - 1100 nm	10 µW - 5 W	Si Integrating w/Baffle	Ø22 mm
		S144C	800 - 1700 nm	100 nW - 500 mW	InGaAs Integrating	Ø5 mm
		S145C	800 - 1700 nm	1 µW - 3 W		Ø22 mm
		S145CL	800 - 1700 nm	10 µW - 3 W	InGaAs Integrating w/Baffle	Ø22 mm
		S146C	900 - 1650 nm	10 µW - 20 W	InGaAs Integrating	Ø12 mm
		S148C	1200 - 2500 nm	1 µW - 1 W		Ø5 mm
		S180C	2900 - 5500 nm	1 µW - 3 W	MCT (HgCdTe)	Ø7 mm
Fiber Sensors	Fiber Power Measurements and Field Applications	S150C	350 - 1100 nm	100 pW - 5 mW	Si Fiber	Ø5 mm
		S151C	400 - 1100 nm	1 nW - 20 mW		Ø5 mm
		S154C	800 - 1700 nm	100 pW - 3 mW	InGaAs Fiber	Ø5 mm
		S155C	800 - 1700 nm	1 nW - 20 mW		Ø5 mm

Sensor Type	Applications	Item #	Wavelength	Energy or Power Range	Detector Type	Aperture	Response Timec
High Resolution	Broadband Measurements of Optical Powers ≤5 W with 1 µW or 5 µW Resolution	S401C	190 nm - 20 µm	10 µW - 1 W (3 Wd)	Thermal Surface Absorber with Background Compensation	Ø10 mm	1.1 s
		S405C	190 nm - 20 µm	100 µW - 5 W	Thermal Surface Absorber	Ø10 mm	1.1 s
Max Power: 10 W	General Broadband Power Measurements of Low and Medium Power Light Sources	S415C	190 nm - 20 µm	2 mW - 10 W (20 Wd)		Ø15 mm	0.6 s
		S425C	190 nm - 20 µm	2 mW - 10 W (20 Wd)		Ø25.4 mm	0.6 s
Max Power: 40 W to 200 W		S350C	190 nm - 1.1 µm, 10.6 µm	10 mW - 40 W (60 Wd)		Ø40 mm	9 s (1 s from 0 to 90%)
		S425C-L	190 nm - 20 µm	2 mW - 50 W (75 Wd)		Ø25.4 mm	0.6 s
		S322C	250 nm - 11 µm	100 mW - 200 W (250 Wd)		Ø25 mm	5 s (1 s from 0 to 90%)
High Max Power Density	Optical Power Measurements of Nd:YAG and Other Pulsed Laser Sources	S370C	400 nm - 5200 nm	10 mW - 10 W (15 Wd)	Thermal Volume Absorber	Ø25 mm	45 s (3 s from 0 to 90%)
		S470C	250 nm - 10.6 µm	100 µW - 5 W		Ø15 mm	6.5 s (<2 s from 0 to 90%)
Microscope Slide	Measure Power at the Sample Plane of a Microscope	S175C	300 nm - 10.6 µm	100 µW - 2 W	Thermal Surface Absorber	18 mm x 18 mm	3 s (<2 s from 0 to 90%)

Sensor Type	Applications	Item #	Wavelength	Power Range	Detector Type	Aperture	Response Timec
High Resolution	Precise Beam Position and Power Measurements of Low and Medium Power Lasers	S440C	190 nm - 20 µm	0.5 mW - 5 W	Thermal Absorber, Four Quadrants	17 x 17 mm	<1.1 s
High Power		S442C	190 nm - 20 µm	10 mW - 50 W	Thermal Absorber, Four Quadrants	Ø17.5 mm	<0.6 s

Sensor Type	Applications	Item #	Wavelength	Energy or Power Range	Max Repetition Rate (@ 1 MΩ Load)	Detector Type	Aperture	Response Time
Standard Energy Sensors	General Purpose Energy Meter	ES111C	185 nm - 25 µm	10 µJ - 150 mJ	40 Hz	Pyroelectric Black Broadband Coating	Ø11 mm	N/Ae
		ES120C	185 nm - 25 µm	100 µJ - 500 mJ	30 Hz		Ø20 mm
		ES145C	185 nm - 25 µm	500 µJ - 2 J	30 Hz		Ø45 mm
High-Energy Sensors	High Energy Measurements for High Peak Energy Lasers: Excimer, CO2-TEA, and Nd:YAG	ES220C	185 nm - 25 µm	500 µJ - 3 J	30 Hz	Pyroelectric Ceramic Coating	Ø20 mm
		ES245C	185 nm - 25 µm	1 mJ - 15 J	30 Hz		Ø45 mm
Fast Energy Sensors	High Repetition Rate Measurements	ES308C	185 nm - 25 µm	500 µJ - 1 J	1 kHz	Pyroelectric Black Broadband Coating	Ø8 mm
		ES312C	185 nm - 25 µm	100 µJ - 1 J	250 Hz		Ø12 mm
		ES408C	185 nm - 2.5 µm	100 µJ - 1 J	10 kHz	Pyroelectric Metal Coating	Ø8 mm
		ES412C	185 nm - 2.5 µm	50 µJ - 500 mJ	2 kHz		Ø12 mm

• The response time of the photodiode sensor. The actual response time of a power meter using these sensors will be limited by the update rate of your power meter console.
• The power 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. Please see the Specs tab here for more details. 
• Typical natural response time (0 - 95%). Our power consoles can provide estimated measurements of optical power on an accelerated time scale (typically <1 s) when the natual response time is approximately 1 s or greater. As the natural response times of the S415C, S425C, and S425C-L are fast, these do not benefit from accelerated measurements and this function cannot be enabled. For more information, see the Operation tab here.
• With intermittent use: maximum exposure time of 20 minutes for the S401C, otherwise maximum exposure time is 2 minutes.
• All pyroelectric sensors have a thermal time constant, τ. This value indicates how long it takes the sensor to recover from a single pulse. To detect the correct energy levels, pulses must be shorter than 0.1τ and the repetition rate of your source must be well below 1/τ. Please see the Specs tab here for the τ value of each sensor.

Figure 113G  Sensor Options Arranged by Wavelength Range

Figure 113H  Sensor Options Arranged by Power Range

Figure 796A  DAkkS-accredited calibrations are performed in accordance with DIN EN ISO/IEC 17025:2018.

Recalibration Services
Thorlabs offers two types of recalibration services in-house for our power and energy meter electronics and photodiode power sensors: ISO 17025 accredited calibrations and manufacturer calibrations. Only the manufacturer calibration is available for the NS170C microscope slide peak power sensor, our thermal power sensors, and our pyroelectric energy sensors. All new products are delivered with a manufacturer calibration by default; if an ISO 17025 accredited calibration is desired for a new device, please contact Tech Sales.

ISO 17025 accredited calibrations are performed in-house in accordance with DIN EN ISO/IEC 17025:2018. Thorlabs GmbH's calibration laboratory is accredited by the German Accreditation Body (DAkkS), the national accreditation authority of the Federal Republic of Germany. The scope of services is described here in English or German. Accredited calibrated power and/or energy meter electronics come with a dedicated certificate of calibration proving the specified accuracy and traceability of calibration data. This certification may be required in certain applications or industries, such as the medical market.

In contrast, our manufacturer calibrations are subject to the quality management requirements of ISO 9001. The certificate of calibration lists the equipment used for the calibration procedure as well as the calibration data acquired. The manufacturer calibration of a power sensor includes recalibration of a single-channel console or interface 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.

Both types of calibration can be offered for third-party equipment or adjusted for special requirements upon request. Please reach out to Tech Sales for further details.

We recommend recalibrating your Thorlabs sensor and console as a pair; however, each may be recalibrated individually. To ensure accurate measurements, we recommend recalibrating annually. To order one or more sensor recalibrations with a dual-channel console, we offer two options: either 1) fill out the Returns Material Authorization (RMA) form with each console and sensor Item # to be recalibrated and specify either manufacturer calibration or ISO 17025 accredited calibration in the "Further Details" field, or 2) separately add each recalibration service Item # offered below to your cart.