Wavelength-selectable laser device providing spatially-selectable wavelenth(s)
A wavelength-selectable laser device providing spatially-selectable wavelength(s) may be used to select one or more wavelengths for lasing in a tunable transmitter or transceiver, for example, in a wavelength division multiplexed (WDM) optical system such as a WDM passive optical network (PON). The wavelength-selectable laser device uses a dispersive optical element, such as a diffraction grating, to disperse light emitted from a laser emitter and to direct different wavelengths of the light toward a reflector at different spatial positions such that the wavelengths may be selected by allowing light to be reflected from selected spatial position(s) back into the laser emitter. Thus, the reflected light with a wavelength at the selected spatial position(s) is allowed to complete the laser cavity.
1. A wavelength-selectable laser device comprising:
a laser emitter for emitting light at a plurality of wavelengths, the laser emitter including a gain region;
a front reflector configured to reflect light from one side of the laser emitter;
a volume phase grating (VPG) for passing the wavelengths such that different wavelengths are directed from the VPG at different angles;
collimating optics for collimating light emitted from the laser emitter and directing the light to the VPG;
a mirror array configured to selectively reflect light from a selected reflective region of the mirror array;
focusing optics for focusing the light passing through the VPG at the different wavelengths onto the mirror array such that the different wavelengths are incident on the mirror array at different respective locations on the mirror array;
wherein a laser cavity is formed between the selected reflected region of the mirror array and the front reflector and including the gain region; and
wherein the front reflector is highly reflective and the laser emitter is configured to provide laser output at the selected wavelength(s) from an opposite side of the laser emitter, and wherein the laser output is passed through the VPG as a zero order direct transmission, and further comprising focusing optics for focusing the zero order direct transmission to couple the laser output at the selected wavelength(s).
2. The wavelength-selectable laser device of claim 1 wherein the tunable filter further comprises control circuitry coupled to the mirror array and configured to control regions of the mirror array that are reflective to control selection of the spatially-selected wavelength reflected back to the laser emitter.
3. The wavelength-selectable laser device of claim 1 wherein the mirror array includes a microelectro-mechanical (MEMS) mirror array.
4. The wavelength-selectable laser device of claim 1 wherein the VPG is fixed such that wavelength selection is provided without moving the VPG.
5. A wavelength division multiplexed (WDM) system comprising:
a plurality of terminals associated with different respective channel wavelengths and configured to transmit optical signals on the different respective channel wavelengths, at least one of the plurality of terminals including at least a tunable optical transmitter configured to be tuned to a respective channel wavelength, the tunable optical transmitter comprising a wavelength-selectable laser device configured to provide spatially-selectable channel wavelengths by reflecting at least one selected channel wavelength based on a spatial location of the channel wavelength and causing the spatially-selected channel wavelength to complete a laser cavity in the laser device, wherein the wavelength-selectable laser device comprises:
a laser emitter for emitting light at a plurality of wavelengths, the laser emitter including a gain region;
a front reflector configured to reflect light from one side of the laser emitter;
a volume phase grating (VPG) for passing the wavelengths such that different wavelengths are directed from the VPG at different angles;
collimating optics for collimating light emitted from the laser emitter and directing the light to the VPG;
a mirror array configured to selectively reflect light from a selected reflective region of the mirror array;
focusing optics for focusing the light passing through the VPG at the different wavelengths onto the mirror array such that the different wavelengths are incident on the mirror array at different respective locations on the mirror array;
wherein a laser cavity is formed between the selected reflected region of the mirror array and the front reflector and including the gain region; and
wherein the front reflector is highly reflective and the laser emitter is configured to provide laser output at the selected wavelength(s) from an opposite side of the laser emitter, and wherein the laser output is passed through the VPG as a zero order direct transmission, and further comprising focusing optics for focusing the zero order direct transmission to couple the laser output at the selected wavelength(s).
6. The WDM system of claim 5 comprising:
at least one central office configured to transmit and receive aggregate WDM optical signals including the channel wavelengths; and
at least one branching point located between the central office and the plurality of terminals, the branching point being configured to combine the optical signals at the channel wavelengths.