US 12,218,485 B2
Mid-IR external cavity quantum cascade laser with a wavelength-adjustable interference filter
Jan F. Kischkat, Berlin (DE)
Appl. No. 16/976,098
Filed by Jan F. Kischkat, Berlin (DE)
PCT Filed Feb. 28, 2019, PCT No. PCT/EP2019/055037
§ 371(c)(1), (2) Date Aug. 27, 2020,
PCT Pub. No. WO2019/166575, PCT Pub. Date Sep. 6, 2019.
Claims priority of application No. 18159180 (EP), filed on Feb. 28, 2018.
Prior Publication US 2020/0412093 A1, Dec. 31, 2020
Int. Cl. H01S 5/14 (2006.01); H01S 5/02325 (2021.01); H01S 5/065 (2006.01); H01S 5/34 (2006.01); H01S 5/0222 (2021.01); H01S 5/024 (2006.01); H01S 5/028 (2006.01); H01S 5/10 (2021.01)
CPC H01S 5/141 (2013.01) [H01S 5/02325 (2021.01); H01S 5/0654 (2013.01); H01S 5/3401 (2013.01); H01S 5/3402 (2013.01); H01S 5/0222 (2013.01); H01S 5/02415 (2013.01); H01S 5/02476 (2013.01); H01S 5/0287 (2013.01); H01S 5/1085 (2013.01); H01S 2302/02 (2013.01)] 13 Claims
OG exemplary drawing
 
1. Wavelength-switchable, semiconductor laser (10), for generating of laser light in the optical mid-infrared range between 3 μm and 50 μm, wherein the laser (10) comprises an external cavity (11) and at least the following components:
a semiconductor optical amplifier (12) comprising a Quantum Cascade Laser, QCL, for the mid-infrared region, comprising an intra-cavity facet (121) facing towards
a first optical element (13) for collimating a laser beam exiting the intra-cavity facet (121) arranged at the intra-cavity facet (121) of the semiconductor optical amplifier (12),
a transmissive, wavelength-adjustable interference filter (1), comprising at least
i) a wavelength-adjustable Fabry-Perot filter (100) and
ii) an etalon (110) comprising a first planar surface (111) and a second planar (112) surface, wherein the first and second surface (111, 112) of the etalon (110) are arranged opposite and plane-parallel to each other and delimit an etalon cavity (113),
an on-axis retro-reflector (14) arranged at one end of the external cavity (11),
wherein the etalon (110) and the Fabry-Perot filter (100) are arranged in a row, wherein the interference filter (1) is arranged between the first optical element (13) and the on-axis retro-reflector (14), and
wherein the components of the interference filter (1) are arranged such that laser light comprising a selected laser wavelength can stably resonate in the external cavity,
wherein the Fabry-Perot filter (100) comprises a first and a second mirror element (101, 102) that are arranged on a micro-electro-mechanical system (201), MEMS, such as to alter the distance (301) between them,
wherein a first reflective layer (103) comprised by the first mirror element (101) and a second reflective layer (104) comprised by of the second mirror element (102) are plane-parallel to each other,
wherein a free spectral range of the etalon for the selected laser wavelength is at least 10 times smaller than a free spectral range of the Fabry-Perot filter for the selected laser wavelength, and
wherein the etalon and the Fabry-Perot filter are arranged such that for an incident light beam comprising the selected laser wavelength, a full-width half-maximum of a transmission band of the selected laser wavelength of the etalon is at least 5 times smaller than the full-width half-maximum of the transmission band of the Fabry-Perot filter.