# US 2014/0192830 A1 · Wavelength locking of a laser device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0192830 A1 - Document ID: US20140192830A1 - Status: Published application - Kind: A1 - Application number: 13/735,418 - Filed: 2013-01-07 - Published: 2014-07-10 - Earliest claimed: 2013-01-07 - Assignees: Emcore Corporation - Inventors: Henry A. Blauvelt; Kerry Vahala - Web page: https://patentgrep.com/patent/US20140192830A1 ## CPC - H01S 3/137: for stabilising of frequency - H01S 5/02326: Arrangements for relative positioning of laser diodes and optical components, e.g. grooves in the mount to fix optical fibres or lenses - H01S 5/0687: Stabilising the frequency of the laser - H01S 5/12: the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers (comprising a photonic bandgap structure H01S5/11; surface-emitting lasers H01S5/18) - H01S 5/02212: Can-type, e.g. TO-CAN housings with emission along or parallel to symmetry axis - H01S 5/02216: Butterfly-type, i.e. with electrode pins extending horizontally from the housings - H01S 5/02251: using optical fibres - H01S 5/02415: {by using a thermo-electric cooler [TEC], e.g. Peltier element} - H01S 5/06804: {by monitoring an external parameter, e.g. temperature} - H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL ## Abstract There is discussed an optical system comprising a laser device that outputs a divergent light beam. A first portion of the divergent light beam, including a central portion, passes through an etalon device, which acts as a wavelength discriminator, and then the central portion is incident on a first monitor photodiode, which generates a wavelength-dependent detection signal. A second portion of the divergent light beam is incident on a second monitor photodetector, without passing through the etalon device, to generate a wavelength-independent detection signal. A processor processes the wavelength-dependent detection signal and the wavelength-independent detection signal to determine a control signal for controlling the wavelength of the laser device. By accurately positioning a photodetector at the central fringe of the divergent light beam following transmission through the etalon device, a compact and cost-effective wavelength locking arrangement is provided. ## Claims ### Claim 1 An optical system comprising: a laser device operable to output a divergent light beam; an etalon device arranged to receive and filter a first uncollimated portion of the divergent light beam; a first monitor photodetector positioned to detect only a central portion of the first uncollimated portion of the divergent light beam, following filtering by the etalon device and to generate a wavelength-dependent detection signal; and a second monitor photodetector operable to detect a second uncollimated portion of the divergent light beam, said second uncollimated portion travelling from the laser device to the second monitor photodetector without passing through the etalon device and to generate a wavelength-independent detection signal. ### Claim 2 (depends on 1) The optical system of claim 1, further comprising a processor operable to process the wavelength-dependent detection signal and the wavelength-independent detection signal to determine a control signal for controlling the wavelength of the laser device. ### Claim 3 (depends on 1) The optical system of claim 1, further comprising a thermoelectric cooler operable to vary the temperature of the laser device in response to said control signal. ### Claim 4 (depends on 1) The optical system of claim 1, wherein the first monitor photodetector is positioned so as to exclude any fringe pattern of the light beam transmitted through the etalon device. ### Claim 5 (depends on 4) The optical system of claim 4, wherein the divergent light beam is centred about an optical axis, the first monitor photodetector and the second monitor photodetector are mounted on a common support, and the first monitor photodiode is tilted at an angle to the optical axis. ### Claim 6 (depends on 5) The optical system of claim 5, wherein said angle is within the range of 5° to 10°. ### Claim 7 (depends on 1) The optical system of claim 1, wherein the laser device, the first photodetector, the etalon device and the second photodetector are mounted on a substrate, wherein the second photodetector is positioned between the laser device and the etalon device; and wherein the divergent light beam is centred on an optical axis which passes through the etalon device. ### Claim 8 (depends on 7) The optical system of claim 7, wherein the laser device is arranged such that the optical axis is parallel to the substrate, and the perpendicular distance between the optical axis and the substrate is greater than the height of the second photodetector above the substrate. ### Claim 9 (depends on 8) The optical system of claim 8, wherein the second photodetector has an active detection surface parallel to a planar surface of the substrate. ### Claim 10 (depends on 1) The optical system of claim 1, wherein the laser device is a semiconductor diode laser. ### Claim 11 An optical module comprising: housing; a laser device positioned in the housing and operable to output a divergent light beam; an optical fiber output arrangement configured to receive a front portion of the divergent light beam for coupling the front portion of the divergent light beam to an optical fiber; and a wavelength locking arrangement configured to receive a rear portion of the divergent light beam for locking the operational wavelength of the laser device to a selected frequency, wherein the wavelength locking arrangement does not comprise a collimating lens, wherein the wavelength locking arrangement comprises: an etalon device arranged to receive and filter a first portion of the rear portion of the divergent light beam; a first monitor photodetector positioned to detect only a central portion of the first portion of the rear portion of the divergent light beam, following filtering by the etalon device and to generate a wavelength-dependent detection signal; and a second monitor photodetector operable to detect a second portion of the rear portion of the divergent light beam, said second portion travelling from the laser device to the second monitor photodetector without passing through the etalon device and to generate a wavelength-independent detection signal. ### Claim 12 (depends on 11) The optical module of claim 11, wherein the housing comprises a butterfly housing. ### Claim 13 (depends on 11) The optical module of claim 11, further comprising a thermoelectric cooler operable to vary the temperature of the laser device. ### Claim 14 (depends on 11) The optical module of claim 11, wherein the first monitor photodetector is positioned so as to exclude any fringe pattern of the light beam transmitted through the etalon device. ### Claim 15 (depends on 14) The optical module of claim 14, wherein the first monitor photodetector and the second monitor photodetector are mounted on a planar surface of a common support, and the first monitor photodiode is tilted at an angle to the planar surface. ### Claim 16 (depends on 15) The optical module of claim 15, wherein said angle is within the range of 5° to 10°. ### Claim 17 (depends on 11) The optical module of claim 11, wherein the laser device, the first photodetector the etalon device and the second photodetector are mounted on a substrate, wherein the second photodetector is positioned between the laser device and the etalon device; and wherein the divergent light beam is centred on an optical axis which passes through the etalon device. ### Claim 18 (depends on 17) The optical module of claim 17, wherein the laser device is arranged such that the divergent light beam is centred on an optical axis that is parallel to the substrate, and the perpendicular distance between the optical axis and the substrate is greater than the height of the second photodetector above the substrate. ### Claim 19 (depends on 18) The optical module of claim 18, wherein the second photodetector has an active detection surface parallel to a planar surface of the substrate. ### Claim 20 (depends on 11) The optical module of claim 11, wherein the laser device is a semiconductor diode laser.