Wavelength-tunable laser device and wavelength control method

A wavelength-tunable laser device comprising:

• a wavelength-tunable light source part configured to tune an emission wavelength of a laser beam using a Vernier effect,
• an optical filter having a periodic transmission characteristic for a wavelength of the laser beam output from the wavelength-tunable light source part;
• a light receiving element configured to acquire intensity of the laser beam transmitted through the optical filter;
• a control device configured to control an operation of the wavelength-tunable light source part;
• and
• a single temperature regulator including a disposition surface on which the wavelength-tunable light source part and the optical filter are disposed, wherein the wavelength-tunable light source part and the optical filter are disposed on the same disposition surface of the single temperature regulator, the single temperature regulator being configured to control a driving condition of the wavelength-tunable light source part to cause a situation in which temperature distribution within the disposition surface changes, thereby causing a temperature of the optical filter to become a first temperature or a second temperature different from the first temperature to change the transmission characteristic of the optical filter, wherein
• the control device comprises:
• a monitor value calculating part configured to calculate a monitor value corresponding to the wavelength of the laser beam based on the intensity of the laser beam acquired by the light receiving element;
• a storage part configured to store a plurality of pieces of wavelength control information;
• a target value calculating part configured to calculate a control target value corresponding to a target wavelength of the laser beam as a target value of the monitor value based on the wavelength control information and the target wavelength;
• and
• a wavelength control part configured to control the wavelength of the laser beam to be the target wavelength based on the control target value and the monitor value, wherein
• the wavelength control information is information in which a wavelength, a control reference value corresponding to the wavelength as a reference value of the monitor value, and mode identification information for identifying a super mode that is determined in a case in which the control reference value is caused to be the control target value are associated with each other, the super mode being a wavelength of a laser beam that an optical resonator in a wavelength-tunable light source part outputs when reflection peaks agree in wavelength, and
• the target value calculating part calculates the control target based on a plurality of pieces of the wavelength control information stored in the storage part in association with the same mode identification information in a case in which the same wavelength as the target wavelength when the control target is not included in the wavelength control information that is stored in the storage unit,
• wherein the target value calculating part calculates, in a case in which the mode identification information is different between first wavelength control information including the wavelength that is adjacent to the target wavelength on either one of a short wave side or a long wave side and second wavelength control information including the wavelength that is adjacent to the target wavelength on another one of the short wave side or the long wave side among the pieces of wavelength control information, the control target value by using a plurality of the control reference values associated with the same mode identification information as the mode identification information of one of the first wavelength control information and the second wavelength control information,
• wherein the target value calculating part calculates, in a case in which the mode identification information is the same as first wavelength control information including the wavelength that is adjacent to the target wavelength on either one of a short wave side or a long wave side and second wavelength control information including the wavelength that is adjacent to the target wavelength on another one of the short wave side or the long wave side among the pieces of wavelength control information, the control target value by using a plurality of the control reference values associated with the same mode identification information, and
• wherein the temperature of the optical filter is the first temperature when the mode identification information is the same, and the temperature of the optical filter is the second temperature when the mode identification information is different.