An intra-cavity doubled OPS-laser has a laser-resonator including a birefringent filter (BRF) for coarse wavelength-selection, and an optically nonlinear (ONL) crystal arranged for type-II frequency-doubling and fine wavelength-selection. Laser-radiation circulates in the laser-resonator at one of a range of fundamental wavelengths dependent on the resonator length. The ONL crystal has a transmission peak-wavelength dependent on the crystal temperature. Reflection of circulating radiation from the BRF is monitored. The reflection is at a minimum when the ONL crystal transmission-peak wavelength is at the circulating radiation wavelength. The temperature of the ONL crystal is selectively varied to maintain the monitored reflection at about a minimum.

A tunable laser has a solid state laser medium having an optical gain region and generates coherent radiation through a facet. A lens collects the coherent radiation and generates a collimated light beam. Components of an external cavity include a reflective surface and an optical filter, the reflective surface reflecting the collimated beam back to the lens and the laser medium, the optical filter positioned between the reflective surface and the lens and having two surfaces with a thermally tunable optical transmission band within the optical gain region of the laser medium. The optical filter (1) transmits a predominant portion of the collimated beam at a desired wavelength of operation, and (2) specularly reflects a remaining portion of the collimated beam from each surface, the collimated beam being incident on the optical filter such that the reflected collimated beams propagate at a non-zero angle with respect to the incident collimated beam.

An optical module and a method of assembling the optical module are disclosed. The optical module comprises a laser unit, a modulator unit, and a detector unit mounted on respective thermo-electric coolers (TECs). The modulator unit, which is arranged on an optical axis of the first output port from which a modulated beam is output, modulates the continuous wave (CW) beam output from the laser unit. On the other hand, the laser unit and the detector unit are arranged on another optical axis of the second output port from which another CW beam is output. The method of assembling the optical module first aligns one of the first combination of the laser unit and the modulator unit with the first output port and the second combination of the laser unit and the detector unit, and then aligns another of the first combination and the second combination.

A quantum cascade laser includes a semiconductor substrate, an optical waveguide formed on a first surface of the semiconductor substrate, and a temperature adjusting member. The optical waveguide includes a first region and a second region located on one side with respect to the first region in the optical waveguide direction of the optical waveguide. The first region generates a first light having a first wavelength, and the second region generates a second light having a second wavelength. The optical waveguide generates an output light having a frequency corresponding to a difference between the first wavelength and the second wavelength by difference-frequency generation. A recess for suppressing heat transfer between the first region and the second region is formed at a second surface of the semiconductor substrate. The temperature adjusting member includes a first temperature adjusting member for adjusting the temperature of the second region.

The purpose of the present invention is to make it possible to output stable light by optimizing the wavelength conversion efficiency in a wavelength conversion element without employing an optical detection device such as a photo diode in a laser light source device. A fundamental light wave emitted from a semiconductor laser (2) is wavelength converted by a wavelength conversion element (5) and is emitted therefrom. A lighting circuit (20) supplies electric power for the aforementioned semiconductor laser (2) to turn on the semiconductor laser (2). A control unit (21) controls the operation of the device while controlling the amount of power supplied to a heater means (7) such that the wavelength conversion element (5) reaches a temperature at which optimum wavelength conversion efficiency is acquired. The temperature detected by a temperature detection means (Th1) is input to the control unit (21), and the control unit (21) defines the temperature of the wavelength conversion element (5) at which the maximum amount of power is supplied to the heater means (7) as a set temperature at which the optimum wavelength conversion efficiency is acquired, and performs feedback control of the temperature of the wavelength conversion element (5) so that the temperature of the wavelength conversion element (5) reaches the aforementioned set temperature by controlling the amount of heat supplied from the heater means (7).

Provided are a tunable wavelength filter with an embedded metal temperature sensor and an external-cavity type tunable wavelength laser module. In detail, the tunable wavelength filter with an embedded metal temperature sensor and the external-cavity type tunable wavelength laser module achieve wavelength stability by forming a metal temperature sensor using a resistance change of a metal thin film according to temperature on a point on an isothermal layer having the same temperature distribution as the optical waveguide during a process for fabricating the optical waveguide with polymer to accurately measure a temperature of an optical waveguide.

An optical transmitter module includes a semiconductor laser device, optical modulator, temperature adjusting device which includes a substrate, a first installation part and a second installation part, a package having a bottom surface opposite to a back surface of the substrate, the package housing the semiconductor laser device, the optical modulator, and the temperature adjusting device; and a middle block disposed between a first temperature controlling element a the second temperature controlling element, the middle block having a back surface directly or indirectly fastened to a principal surface of the substrate.

A driving and stabilization system for a pump laser, and a pump laser system. The driving and stabilization system includes a constant current stabilization device, a constant temperature stabilization device, a power detection device, an environment detection device, and a control device. The constant current stabilization device includes a voltage comparison circuit, a constant current driving circuit, and a switch protection circuit. The constant temperature stabilization device includes an internal constant temperature stabilization circuit and an external constant temperature stabilization circuit.

A semiconductor laser device includes: a plurality of semiconductor light emitting elements each of which emits a light beam; a wavelength dispersion element (a diffraction grating) that emits the light beam emitted from each of the plurality of semiconductor light emitting elements to pass through one optical path; a pedestal that supports the wavelength dispersion element; and a presser that fixes the wavelength dispersion element to the pedestal by pressing the wavelength dispersion element. The presser presses on the wavelength dispersion element in a direction perpendicular to a surface on which with the wavelength dispersion element is provided.

A tunable laser has a solid state laser medium with optical gain region and generates coherent radiation through a facet. A lens collects the coherent radiation and generates a collimated light beam. An external cavity includes a reflective surface and an optical filter, the reflective surface reflecting the collimated beam back to the lens and laser medium, the optical filter positioned between the reflective surface and the lens and having two surfaces and a thermally tunable optical transmission band within the optical gain region of the laser medium. The optical filter (1) transmits a predominant portion of the collimated beam at a desired wavelength of operation, and (2) specularly reflects a remaining portion of the collimated beam from each surface, the collimated beam being incident on the optical filter such that the reflected collimated beams propagate at a non-zero angle with respect to the incident collimated beam.