Picosecond Gain-Switched Lasers

  • Center Wavelengths from 450 to 1550 nm
  • Picosecond Pulses, Nanosecond Pulses, or CW Operation
  • <130 ps Pulse Widths and Repetition Rates up to 200 MHz
  • Compact Laser Systems with Fiber-Coupled Output


1064 nm Picosecond
Gain-Switched Laser






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Key Specificationsa
Item # Center
Avg. Powerd
GSL45A 450 ± 10 nm <90 ps >32 mW >0.6 mW
1 to 65 ns 12 mW -
GSL49A 488 ± 10 nm <120 ps >29 mW >0.7 mW
1 to 65 ns 12 mW -
GSL52A 520 ± 10 nm <120 ps >40 mW >1.0 mW
1 to 65 ns 15 mW -
GSL63A 633 ± 10 nm <130 ps >75 mW >2.0 mW
1 to 65 ns 35 mW -
GSL85A 850 ± 10 nm <70 ps >86 mW >1.2 mW
1 to 65 ns 37.5 mW
GSL106A 1064 ± 10 nm <100 ps >35 mW >0.7 mW
1 to 65 ns 25 mW -
GSL131A 1310 ± 20 nm <80 ps >43 mW >0.7 mW
2 to 65 ns 37.5 mW -
GSL155A 1550 ± 20 nm <80 ps >37 mW >0.6 mW
2 to 65 ns 30 mW -
  • Refer to the Specs tab for complete specifications.
  • Pulse widths are of fixed duration and adjustable over 15 discrete settings, from the minimum to the maximum specified width. Refer to the Specs tab for plots of typical pulses.
  • This value is a typical max for picosecond pulses and is typical for nanosecond pulses.
  • Specification is given for operation at 200 MHz.


  • Fluorescence Lifetime Imaging
  • Time-Resolved Imaging
  • Fiber Amplifier Seed Source
  • Impulse Test and Measurement
  • Quantum Key Distribution


  • 450 nm to 1550 nm Center Wavelengths
  • <130 ps Pulse Width, 1 to 65 ns Pulse Widths, and CW Operation
  • Fiber-Coupled Output with FC/APC Connector
  • Precision Patch Cables Included for Lasers with Center Wavelengths ≤1064 nm
  • Integrated Drive and Temperature Control Electronics
  • Trigger Output for Pulse Synchronization
  • Internal and External Triggering from Single Shot to 200 MHz

Thorlabs' GSL Series Gain-Switched Lasers provide picosecond, nanosecond, and continuous wave operation in compact, fiber-coupled, turnkey sources. Gain-switched pulse generation with adjustable pulse widths and repetition rates up to 200 MHz make these lasers suitable for high-speed imaging, fluorescence lifetime measurements, and impulse testing. GSL series lasers are also ideal seed sources for additional amplification using our range of fiber-based amplifiers.

The drive electronics and temperature control circuits for the laser diode are integrated into each device and are powered by an included DS15 power supply with region-specific plug. Single-mode fiber output through an FC/APC connector allows for integration with a wide range of fiber-terminated devices.

Patch Cables with Precision Connectors
GSL series lasers with mode-field diameters <7 μm include a fiber patch cable with precision connectors (Item #s GSL45A, GSL49A, GSL52A, GSL63A, GSL85A, GSL106A). Please see the Precision Patch Cables tab for details.

Pulse Width & Repetition Rate Controls
Each GSL series laser offers a control for varying the pulse width between picosecond operation (<130 ps), nanosecond operation adjustable over 14 discrete settings (1 to 65 ns), and continuous wave operation. Single shot operation is also available for pulse widths ≥6 ns. The pulse width control, located on the back panel, directly programs the pulse generator and can be adjusted to one of 16 positions using the included 2.5 mm screwdriver. Plots of typical pulse waveforms and typical pulse width as a function of the pulse width control setting are available in the Specs tab.

Alongside the pulse width control, the repetition rate control provides access to four internal and two external trigger settings, accommodating both Hi-Z and 50 Ω impedance connections. The internally available rates are 1 MHz, 10 MHz, 100 MHz, and 200 MHz. Use the included 2.5 mm flathead screwdriver to select the desired trigger setting. Note that pulse widths longer than 2 ns have maximum frequencies lower than 200 MHz, as illustrated in the diagram on the Specs tabs as well as in Section 4.5 of the manual.

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The female SMA Trigger In/Out port on the back panel has dual functions. If the internal oscillators are used, then the trigger port provides an output signal that is synchronized with the pulse generation. In the user-triggered mode, the SMA port allows external trigger signals to drive the pulse generator. Both a Hi-Z and 50 Ω user-triggered mode are available for low-frequency and high-frequency operation respectively.

Additional Front & Back Panel Features
A dual color (red/blue) emission LED on the front panel indicates when laser output is enabled and is designed to be visible through most laser safety glasses.

In addition to the trigger port, pulse width control, and repetition rate control, a multicolor status LED on the back panel indicates the operation state, including temperature stabilization and any errors. An engraved reference for the repetition rate options is also provided. Please see the Front & Back Panels tab and manual for more details about these features.

The GSL series lasers have built-in safety features including a key switch, interlock pin, and a four-second delay between the emission LED illuminating and laser output.

Electrical Connections
An external DS15 power supply with region-specific plugs is included with each laser. The laser integrates all other required drive electronics, safety interlocks, and temperature stabilization needed for operation; a block diagram with more details can be found on the Specs tab.

Optical Specifications
Center Wavelength 450 ±10 nm 488 ± 10 nm 520 ±10 nm 633 ± 10 nm 850 ± 10 nm 1064 ± 10 nm 1310 ± 20 nm 1550 ± 20 nm
Fiber Typea 460HP 460HP 460HP SM600 780HP HI1060 SMF-28 Ultra SMF-28 Ultra
Laser Class 3B 3B 3B 3B 3B 3B 1M 1M
Output Connector FC/APC, 2.0 mm Narrow Key
Picosecond Pulse Operation
Average Powerb >0.6 mW >0.7 mW >1.0 mW >2.0 mW >1.2 mW >0.7 mW >0.7 mW >0.6 mW
Pulse Durationc <90 ps <120 ps <120 ps <130 ps <70 ps <100 ps <80 ps <80 ps
Spectral Linewidth <3 nm <4 nm <6 nm <3 nm <5 nm <15 nm <12 nm <20 nm
Repetition Rates 200 kHz - 200 MHz
Peak Power (Typ. Max) >32 mW >29 mW >40 mW >75 mW >86 mW >35 mW >43 mW >37 mW
Power Stabilityd <2% Over 8 Hours
Nanosecond Pulse Operation
Pulse Durationsc 1 - 65 ns 2 - 65 ns
Repetition Rates Refer to the Graphic Belowe
Peak Power (Typical) 12 mW 12 mW 15 mW 35 mW 37.5 mW 25 mW 37.5 mW 30 mW
Continuous Wave (CW) Operation
Average Power 3 mW 5 mW 5 mW 15 mW 20 mW
Typical Performance Plots (Click to View Plot)
Typical Pulses <130 ps
1 - 65 ns
Output Spectra <130 ps
1 - 2 ns
Pulse Width Control
  • The fiber output is an FC/APC connector with a narrow 2.0 mm key. GSL series lasers with mode-field diameters <7 μm include a fiber patch cable with precision connectors, (Item #s GSL45A, GSL49A, GSL52A, GSL63A, GSL85A, and GSL106A).
  • Specification is given for operation at 200 MHz.
  • Pulse widths are of fixed duration and adjustable over 15 discrete settings, from the minimum to the maximum specified width. Refer to the Typical Pulses row above for plots of typical pulses and to the graphic below for selectable pulse widths and available repetition rate ranges for each pulse width setting.
  • Stability is the RMS measurement of average power over an 8-hour period of operation.
  • The graphic below shows repetition rate ranges for each pulse width setting. A 40% duty cycle limits the range of operation for longer pulses. This information is presented in tabular format in the Section 4.5 of the manual.
GSL Block Diagram
Click to Enlarge

The graphic above illustrates possible repetition rate ranges for each pulse width setting.
If the externally or internally provided repetition rate is outside of this range,
the Status LED on the rear of the device will flash amber.
Trigger Specifications
Max Input Frequencya 200 MHz
Input Voltageb 50 Ω (AC Coupled)c
0.2 - 5.0 Vpp
Hi-Z, 5 kΩ (DC Coupled) VIL = 0 - 0.8 V
VIH = 2.2 - 5 V
Output Voltage 50 Ω 400 mV
Hi-Z 800 mV
Max Timing Jitterd 12 ps RMS
Delay from External Trigger Input to Optical Outpute 44 ± 4 ns
Delay from Internal Trigger Output to Optical Outpute 3.4 ± 1.5 ns
  • The maximum supported edge transition time is 1 ms.
  • This is set using the Repetition Rate dial on the back panel of the laser.
  • This setting is intended for high frequency operation > 1 MHz; its minimum cutoff frequency is 318 Hz.
  • This applies to external and internal triggering.
  • Trigger delay is measured between the Trigger SMA connector and the optical output at the fiber connector.
GSL Block Diagram
Click to Enlarge

Block diagram depicting the internal architecture of the laser control system with drive electronics, safety interlocks, and temperature stabilization. The multicolored status LED indicator (red/green/amber) blinks during the 30 to 60 s warm up and glows continuously once temperature stability has been achieved.
Power, Environmental, and Physical Specifications
AC Input Frequency Range to DS15 Power Supply 50 - 60 Hz
AC Input Voltage to DS15 Power Supply 100 - 240 V
DC Input Voltage Range to Laser 14.5 - 15.5 V
DC Input Current to Laser 1100 mA Max
Operating Temperature Range 10 to 45 °C
Storage Temperature Range 0 to 60 °C
Humidity Range (RH) 5% to 85%
Mass (Weight) 0.80 kg (1.76 lbs)
Dimensions (L x W x H) 185.6 mm x 100.0 mm x 39.4 mm
(7.31" x 3.94" x 1.55")

GSL Series Laser System Front and Back Panels

Front Panel
Call Out Description
1 Laser Emission Status LED, Dual Color (Red/Blue)
2 FC/APC Fiber Bulkhead, 2.0 mm Narrow Key
Back Panel
Call Out Description
1 Power Key Switch
2 Male Mini-XLR Connector for the +15 V Power Supply Jack
3 Laser Status Indicator LED, Tri-Color (Red/Green/Amber)
4 Pulse Width Selectora
5 Repetition Rate Selectora
6 Trigger In/Trigger Out (Female SMA Connector)
7 Interlock Jack, 2.5 mm Mono Phono (Interlock Pin Installed)
8 Chart of Repetition Rate Options vs. Selector Settings
  • Adjustable using the included 2.5 mm flathead screwdriver.

Precision Patch Cables

Visible wavelengths present a challenge when attempting to mate together single-mode fibers. With mode-field diameters (MFD) less than 7 μm in these fibers, small deviations in core location can result in significant insertion loss. For example: in 460HP fiber with an MFD of 3.5 µm and operating at λ = 450 nm, a 1 µm misalignment can result in 1.5 dB of calculated insertion loss. To solve this challenge, we have provided pigtailed lasers with precision-located centers and matched patch cables that result in lower insertion loss. It should be noted that these improvements are not guaranteed when combined with standard fiber patch cables.

Fiber Specifications
Item # Fiber Type Mode-Field Diameter  Includes Patch Cable
GSL45A 460HP 3.5 ± 0.5 µm @ 515 nm Yes
GSL63A SM600
3.6 to 5.3 µm @ 633 nma Yes
GSL85A 780HP
5.0 ± 0.5 µm @ 850 nm Yes
GSL106A HI1060
6.2 ± 0.3 µm @ 1060 nm Yes
GSL131A SMF-28 Ultra
9.2 ± 0.4 µm @ 1310 nm No
GSL155A 10.4 ± 0.5 µm @ 1550 nm
  • MFD is a nominal, calculated value, estimated at the operating wavelength(s) using a typical value of NA & cutoff wavelength.
Click to Enlarge

Included patch cable is 1 m long with a Ø2 mm jacket.

Fiber Patch Cable Mating for the GSL Series Lasers

The precision patch cables provided for these smaller MFD fibers have a highly centered core in a tight fitting ferrule, which has an inner diameter that closely matches the cladding diameter of the cable's terminated fiber. These two improvements avoid the core misalignment illustrated in the image to the lower left. The image on the lower right highlights the relative size difference between the SMF-28 Ultra and 460HP fibers, which have MFDs of 10.4 µm and 3.5 µm, respectively. The larger MFD of the SMF-28 Ultra fiber can accommodate a small amount of core misalignment without resulting in significant losses, while a smaller MFD requires tighter specifications on the core location to keep insertion losses low.

Click to Enlarge

Relative mode-field diameters are shown for SMF-28 Ultra and 460HP. 
Click to Enlarge

Imperfect core centration in the fiber connector can result in high insertion loss when mating fibers (image not to scale).

Laser Safety and Classification

Safe practices and proper usage of safety equipment should be taken into consideration when operating lasers. The eye is susceptible to injury, even from very low levels of laser light. Thorlabs offers a range of laser safety accessories that can be used to reduce the risk of accidents or injuries. Laser emission in the visible and near infrared spectral ranges has the greatest potential for retinal injury, as the cornea and lens are transparent to those wavelengths, and the lens can focus the laser energy onto the retina. 

Laser Glasses Laser Curtains Blackout Materials
Enclosure Systems Laser Viewing Cards Alignment Tools
Shutter and Controllers Laser Safety Signs

Safe Practices and Light Safety Accessories

  • Laser safety eyewear must be worn whenever working with Class 3 or 4 lasers.
  • Regardless of laser class, Thorlabs recommends the use of laser safety eyewear whenever working with laser beams with non-negligible powers, since metallic tools such as screwdrivers can accidentally redirect a beam.
  • Laser goggles designed for specific wavelengths should be clearly available near laser setups to protect the wearer from unintentional laser reflections.
  • Goggles are marked with the wavelength range over which protection is afforded and the minimum optical density within that range.
  • Laser Safety Curtains and Laser Safety Fabric shield other parts of the lab from high energy lasers.
  • Blackout Materials can prevent direct or reflected light from leaving the experimental setup area.
  • Thorlabs' Enclosure Systems can be used to contain optical setups to isolate or minimize laser hazards.
  • A fiber-pigtailed laser should always be turned off before connecting it to or disconnecting it from another fiber, especially when the laser is at power levels above 10 mW.
  • All beams should be terminated at the edge of the table, and laboratory doors should be closed whenever a laser is in use.
  • Do not place laser beams at eye level.
  • Carry out experiments on an optical table such that all laser beams travel horizontally.
  • Remove unnecessary reflective items such as reflective jewelry (e.g., rings, watches, etc.) while working near the beam path.
  • Be aware that lenses and other optical devices may reflect a portion of the incident beam from the front or rear surface.
  • Operate a laser at the minimum power necessary for any operation.
  • If possible, reduce the output power of a laser during alignment procedures.
  • Use beam shutters and filters to reduce the beam power.
  • Post appropriate warning signs or labels near laser setups or rooms.
  • Use a laser sign with a lightbox if operating Class 3R or 4 lasers (i.e., lasers requiring the use of a safety interlock).
  • Do not use Laser Viewing Cards in place of a proper Beam Trap.


Laser Classification

Lasers are categorized into different classes according to their ability to cause eye and other damage. The International Electrotechnical Commission (IEC) is a global organization that prepares and publishes international standards for all electrical, electronic, and related technologies. The IEC document 60825-1 outlines the safety of laser products. A description of each class of laser is given below:

Class Description Warning Label
1 This class of laser is safe under all conditions of normal use, including use with optical instruments for intrabeam viewing. Lasers in this class do not emit radiation at levels that may cause injury during normal operation, and therefore the maximum permissible exposure (MPE) cannot be exceeded. Class 1 lasers can also include enclosed, high-power lasers where exposure to the radiation is not possible without opening or shutting down the laser.  Class 1
1M Class 1M lasers are safe except when used in conjunction with optical components such as telescopes and microscopes. Lasers belonging to this class emit large-diameter or divergent beams, and the MPE cannot normally be exceeded unless focusing or imaging optics are used to narrow the beam. However, if the beam is refocused, the hazard may be increased and the class may be changed accordingly.  Class 1M
2 Class 2 lasers, which are limited to 1 mW of visible continuous-wave radiation, are safe because the blink reflex will limit the exposure in the eye to 0.25 seconds. This category only applies to visible radiation (400 - 700 nm).  Class 2
2M Because of the blink reflex, this class of laser is classified as safe as long as the beam is not viewed through optical instruments. This laser class also applies to larger-diameter or diverging laser beams.  Class 2M
3R Class 3R lasers produce visible and invisible light that is hazardous under direct and specular-reflection viewing conditions. Eye injuries may occur if you directly view the beam, especially when using optical instruments. Lasers in this class are considered safe as long as they are handled with restricted beam viewing. The MPE can be exceeded with this class of laser; however, this presents a low risk level to injury. Visible, continuous-wave lasers in this class are limited to 5 mW of output power.  Class 3R
3B Class 3B lasers are hazardous to the eye if exposed directly. Diffuse reflections are usually not harmful, but may be when using higher-power Class 3B lasers. Safe handling of devices in this class includes wearing protective eyewear where direct viewing of the laser beam may occur. Lasers of this class must be equipped with a key switch and a safety interlock; moreover, laser safety signs should be used, such that the laser cannot be used without the safety light turning on. Laser products with power output near the upper range of Class 3B may also cause skin burns.  Class 3B
4 This class of laser may cause damage to the skin, and also to the eye, even from the viewing of diffuse reflections. These hazards may also apply to indirect or non-specular reflections of the beam, even from apparently matte surfaces. Great care must be taken when handling these lasers. They also represent a fire risk, because they may ignite combustible material. Class 4 lasers must be equipped with a key switch and a safety interlock.  Class 4
All class 2 lasers (and higher) must display, in addition to the corresponding sign above, this triangular warning sign.  Warning Symbol

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. 



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:
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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Picosecond Gain-Switched Lasers

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GSL45A Support Documentation
GSL45A450 nm Picosecond Gain-Switched Laser, Pulse Widths: <90 ps & 1 to 65 ns
Lead Time
GSL49A Support Documentation
GSL49A488 nm Picosecond Gain-Switched Laser, Pulse Widths: <120 ps & 1 to 65 ns
GSL52A Support Documentation
GSL52A520 nm Picosecond Gain-Switched Laser, Pulse Widths: <120 ps & 1 to 65 ns
GSL63A Support Documentation
GSL63A633 nm Picosecond Gain-Switched Laser, Pulse Widths: <130 ps & 1 to 65 ns
GSL85A Support Documentation
GSL85A850 nm Picosecond Gain-Switched Laser, Pulse Widths: <70 ps & 1 to 65 ns
GSL106A Support Documentation
GSL106A1064 nm Picosecond Gain-Switched Laser, Pulse Widths: <100 ps & 1 to 65 ns
GSL131A Support Documentation
GSL131A1310 nm Picosecond Gain-Switched Laser, Pulse Widths: <80 ps & 2 to 65 ns
GSL155A Support Documentation
GSL155A1550 nm Picosecond Gain-Switched Laser, Pulse Widths: <80 ps & 2 to 65 ns