Mode-hop free laser module

A method of tuning wavelengths of an external cavity laser module, the method comprising:

• emitting a laser beam by a gain chip of the external cavity laser module, wherein
• the gain chip has a front-end and a back-end,
• the front-end is coated with an anti-reflective material,
• the back-end is coated with a reflective material,
• the external cavity laser module comprises:
• the gain chip;
• a first temperature sensor coupled to the gain chip;
• a case that encompasses the gain chip and the first temperature sensor;
• a second temperature sensor adhered to the case;
• a first submount that is formed of a thermally conductive material wherein the gain chip is mounted on the first submount;
• a grating element optically coupled to the gain chip, wherein
• the grating element is configured to receive the laser beam from the gain chip,
• the grating element comprises a diffraction grating, and
• the diffraction grating reflects first wavelengths of a plurality of wavelengths of the laser beam into the gain chip and transmits second wavelengths of the plurality of wavelengths of the laser beam to emit an output beam from the external cavity laser module;
• an external cavity formed between the gain chip and the diffraction grating, wherein the external cavity facilitates optical coupling of the gain chip to the grating element:
• a thermoelectric cooler (TEC) coupled to the first temperature sensor and the second temperature sensor:
• a heatsink mounted on the TEC, wherein
• the first submount is mounted on the heatsink, and
• the heatsink is configured to transfer heat between the first submount and the TEC;
• and
• a second submount mounted on the heatsink, wherein
• the grating element is mounted on the second submount, and
• the second submount thermally isolates the grating element from the heatsink;
• measuring a temperature of the gain chip by the first temperature sensor;
• measuring a temperature of the case by the second temperature sensor;
• varying, by the TEC based on a first temperature value, the temperature of the gain chip when the temperature of the case is a second temperature value, wherein the first temperature value is a mean of two temperature values, of a plurality of temperature values, corresponding to thermistor resistance values of the first temperature sensor;
• and
• tuning, by the TEC, the plurality of wavelengths of the laser beam based on the variation of the temperature of the gain chip, wherein
• the emission of the laser beam from the gain chip is based on the tunned plurality of wavelengths of the laser beam, and
• the laser beam emitted from the gain chip is mode-hop free within the two temperature values of the plurality of temperature values.