External resonance type laser module, analysis apparatus, method of driving external resonance type laser module, and non-transitory computer readable medium
An external resonance type laser module includes a quantum cascade laser, a MEMS diffraction grating configured to include a diffraction/reflection portion configured to diffract and reflect light emitted from the quantum cascade laser and return a part of the light to the quantum cascade laser by swinging the diffraction/reflection portion, and a controller configured to control driving of the quantum cascade laser. The controller is configured to pulse-drive the quantum cascade laser such that pulsed light of a second frequency higher than a first frequency at which the diffraction/reflection portion swings is emitted from the quantum cascade laser and a phase of the pulsed light changes each time the diffraction/reflection portion reciprocates m times (m: an integer of 1 or more).
1. An external resonance type laser module comprising:
a quantum cascade laser;
a MEMS diffraction grating configured to include a diffraction/reflection portion that diffracts and reflects light emitted from the quantum cascade laser and to return a part of the light to the quantum cascade laser by swinging the diffraction/reflection portion; and
a controller configured to control driving of the quantum cascade laser,
wherein the controller is configured to pulse-drive the quantum cascade laser such that pulsed light of a second frequency higher than a first frequency at which the diffraction/reflection portion swings is emitted from the quantum cascade laser, and
wherein the controller is configured to pulse-drive the quantum cascade laser such that a phase of the pulsed light changes each time the diffraction/reflection portion reciprocates m times, where m is an integer of 1 or more.
2. The external resonance type laser module according to claim 1 , wherein the controller is configured to pulse-drive the quantum cascade laser such that the phase of the pulsed light changes by a predetermined value each time the diffraction/reflection portion reciprocates m times.
3. The external resonance type laser module according to claim 2 , wherein the predetermined value is equal to a pulse width of the pulsed light.
4. The external resonance type laser module according to claim 1 , wherein the controller is configured to pulse-drive the quantum cascade laser such that a point in time at which the pulsed light rises coincides with a point in time at which the diffraction/reflection portion turns back in an initial phase.
5. The external resonance type laser module according to claim 1 , wherein the MEMS diffraction grating further includes
a movable portion with which the diffraction/reflection portion is provided,
a support to which the movable portion is swingably coupled, and
an actuator portion configured to swing the movable portion.
6. An analysis apparatus comprising:
the external resonance type laser module according to claim 1 ;
a photodetector configured to detect light output from the external resonance type laser module and transmitted through an analysis target; and
a calculation unit configured to calculate an absorption spectrum based on a detection result of the photodetector,
wherein the calculation unit is configured to calculate the absorption spectrum based on third data obtained by reversing first data obtained by the photodetector in one of a forward path period and a backward path period in swing of the diffraction/reflection portion with respect to time based on a point in time at which the forward path period and the backward path period are switched, and superimposing the first data on second data obtained by the photodetector in the other one of the forward path period and the backward path period.
7. A method of driving an external resonance type laser module, the external resonance type laser module including a quantum cascade laser and a MEMS diffraction grating configured to include a diffraction/reflection portion that diffracts and reflects light emitted from the quantum cascade laser and to return a part of the light to the quantum cascade laser by swinging the diffraction/reflection portion, the method comprising:
pulse-driving the quantum cascade laser such that pulsed light of a second frequency higher than a first frequency at which the diffraction/reflection portion swings is emitted from the quantum cascade laser; and
pulse-driving the quantum cascade laser such that a phase of the pulsed light changes each time the diffraction/reflection portion reciprocates m times, where m is an integer of 1 or more.
8. A non-transitory computer readable medium that stores a program for controlling driving of a quantum cascade laser in an external resonance type laser module including the quantum cascade laser and a MEMS diffraction grating configured to include a diffraction/reflection portion that diffracts and reflects light emitted from the quantum cascade laser and to return a part of the light to the quantum cascade laser by swinging the diffraction/reflection portion,
wherein the program is configured to cause a computer to function as a controller that pulse-drives the quantum cascade laser such that pulsed light of a second frequency higher than a first frequency at which the diffraction/reflection portion swings is emitted from the quantum cascade laser and a phase of the pulsed light changes each time the diffraction/reflection portion reciprocates m times, where m is an integer of 1 or more.