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, contact us for a customized solution.
Part number indentification:
Typical parameters* of gain-modules
* - @ CW, 25C heatsink temperature, external cavity in Littrow configuration with ≈50% feedback