Products - Gain-modules (GM)

External cavity scheme used for device characterization
External cavity scheme (top view)
(top view)

External cavity scheme (side view)
(side view)

The Gain-Module is a similar device to the Gain-Chip, but has one side coupled into single mode fiber. It is greatly applicable for building tunable lasers with a fiber output. Factory made fiber coupling ensures optimized coupling efficiency, long-term stability and excellent reliability. The Gain-Module eliminates the need for a number of components typically used in schemes with a bare Gain-Chip, thus substantially improving system reliability and reducing costs. A further feature of the Gain-module is temperature stability due to the built-in TEC and a high precision thermistor.

The device comprises a Gain-chip of "Type C" with a curved stripe. The facet where the stripe is tilted is designed for external feedback and features deep AR coating, resulting in extremely low back-reflection to the chip waveguide. It ensures the blocking of self-lasing and as well eliminates issues related to the compound cavity when operating in the external cavity system. This results in a very fine spectral line with high Side-Mode Suppression Ratio (SMSR) inherent across the full tuning range. The facet with a perpendicular stripe has the appropriate reflection (typically in the range of 5-15%) to simultaneously provide broad wavelength tuning with high output power. Reflection of this facet in a standard device is optimized for operation in an external cavity setup which provides efficient feedback (about 50%) to the chip (schematically shown in the picture). For schemes with lower feedback, we would recommend a customized device with a different coating on the facet to provide optimized reflection.

Tips for designing the external cavity:

  • it is recommended to use a blazed grating in order to minimize loss to other reflection orders;
  • in case of a grating with higher efficiency in polarization orthogonal to grooves, it is recommended to use λ/2 plate for the combination of high wavelength resolution with the best reflection efficiency.

Note: The operating wavelength, facet reflection and other parameters can be optimized for a particular application and design of external cavity system. Our knowledgeable Application Team is ready to consult and advise on the optimal solution based on your needs and application. Please, for a customized solution.

Part number indentification:


  • 1030 - central wavelength of tuning range (nm)
  • 130 - tuning range width (nm)
  • YY - type of fiber: polarization maintaining (PM) or HI (non PM)
  • 200 - ex-fiber optical power in external cavity (mW)

Available fibers:

  • PM780
  • PM980
  • PM1300
non PM:
  • 780-HP
  • HI1060
  • SMF-28

Gain-module with open back wall
for external free-space feedback

Typical parameters* of gain-modules

Part number Central
of tuning
of maximum
Output power
ex fiber
Fast axis
Slow axis
nm nm nm mW deg deg dB mm mA
GM-1030-150-YY-150 1030 150 1060 150 36 7 0.3 1.4 400
GM-1030-130-YY-200 1030 130 1050 200 19 7 0.2 2.8 400
GM-1060-150-YY-250 1060 150 1100 280 16 6.5 0.1 3 600
GM-1140-120-YY-130 1140 120 1170 130 39 6 0.05 3 600

* - @ CW, 25C heatsink temperature, external cavity in Littrow configuration with ≈50% feedback

Any customized wavelength from the 780-1330 nm range is possible. Please, for the details.