Optical transmitter comprising a stepwise tunable laser
First Claim
1. A stepwise tunable external cavity laser, comprising an optical resonator, the resonator comprising:
- a semiconductor amplifying mirror having a selected gain wavelength band and forming a first end of an optical resonator;
an external mirror forming a second end of the optical resonator, the external mirror being positioned such that a frequency comb of the optical resonator provides is aligned to a predetermined optical channel spacing arrangement; and
an electronically-actuated, frequency selective element, positioned within the optical resonator and having a control input to select an emission wavelength, of an optical beam emitted by the laser.
1 Assignment
0 Petitions
Accused Products
Abstract
An optical fiber transmitter for emitting an information-carrying laser beam comprises an optically or electrically pumped single mode MQW (multi quantum well) semiconductor amplifying mirror as a gain medium and a separate external reflector to form a cavity. The external cavity length defines a comb of optical modes, all or a subset of which corresponding to channel wavelengths of an optical telecommunications system having plural optical channels. The semiconductor gain element has a homogeneously broadened gain region; a tuning arrangement tunes the laser from mode to mode across the gain region thereby selecting each one of the plural optical channels. When the maximum gain bandwidth is less than mode-to-mode spacing defined by the cavity, that tuning arrangement comprises a means of altering the temperature of the amplifying mirror, thereby translating the frequency of the gain peak from one mode to another. An optical modulator adds modulation to a beam emitting from the laser to provide the information-carrying laser beam, and a coupler couples the information-carrying laser beam into an optical fiber of the optical telecommunications system. A calibration method based on detecting inter-mode optical transitions (mode hopping) is described. The parameters of the amplifying mirror and tuning arrangement can be adjusted during operation to switch quickly from one cavity mode to another in stepwise fashion.
-
Citations
20 Claims
-
1. A stepwise tunable external cavity laser, comprising an optical resonator, the resonator comprising:
-
a semiconductor amplifying mirror having a selected gain wavelength band and forming a first end of an optical resonator;
an external mirror forming a second end of the optical resonator, the external mirror being positioned such that a frequency comb of the optical resonator provides is aligned to a predetermined optical channel spacing arrangement; and
an electronically-actuated, frequency selective element, positioned within the optical resonator and having a control input to select an emission wavelength, of an optical beam emitted by the laser. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
a polarization selective element having a high transmission axis;
a birefringent electro-optical medium with an ordinary axis and an extraordinary axis oriented at substantially +45° and
at −
45°
respectively, with respect to the high transmission axis of the polarization selective element; and
voltage means for applying a selected voltage to the electro-optical medium, and for varying the selected voltage over a range of values that includes said gain wavelength band.
-
-
17. The laser of claim 1, wherein said frequency selective element comprises:
-
a polarization selective element having a high transmission axis;
a first birefringent electro-optical medium with an ordinary axis and an extraordinary axis oriented at substantially +45° and
−
45°
, respectively, with respect to the high transmission axis of the polarization selective element;
a second birefringent electro-optical medium with an ordinary axis and an extraordinary axis oriented so that the extraordinary axis of the second electro-optic medium is substantially aligned with the ordinary axis of the first electro-optic medium, and the ordinary axis of the second electro-optic medium is substantially aligned with the extraordinary axis of the first electro-optic medium; and
voltage means for applying a first selected voltage to the first electro-optical medium, for applying a second selected voltage to the second electro-optical medium, and for varying at least one of the first and second selected voltages over a range of values that includes said gain wavelength band, whereby a total length of electro-optic media in said laser can be increased without reducing a laser tuning range, thereby allowing use of at least one of a reduced first selected voltage and a reduced second selected voltage.
-
-
18. The laser of claim 1, wherein said frequency selective element comprises:
-
a polarization selective element having a high transmission axis;
a first birefringent electro-optical medium with an ordinary axis and an extraordinary axis oriented at substantially +45° and
at −
45°
, respectively, with respect to the high transmission axis of the polarization selective element;
a second birefringent electro-optical medium with an ordinary axis and an extraordinary axis oriented such that the extraordinary axis of the second electro-optic medium is substantially aligned with the extraordinary axis of the first electro-optic medium, and the ordinary axis of the second electro-optic medium is substantially aligned with the ordinary axis of the first electro-optic medium;
a half-wave plate, positioned between the first electro-optic medium and the second electro-optic medium, oriented such that light polarized along an ordinary axis of the first electro-optical medium is substantially converted to light polarized along an extraordinary axis of the second electro-optical medium, and light polarized along an extraordinary axis of the first electro-optical medium is substantially converted to light polarized along an ordinary axis of the second electro-optical medium, in transmission through the half wave plate; and
voltage means for applying a first selected voltage to the first electro-optical medium and for applying a second selected voltage to the second electro-optical medium, and for varying at least one of the first and second selected voltages over a range of values that includes said gain wavelength band, whereby an angular bandwidth of said frequency selective element is enhanced, and a total length of the electro-optic media in said laser can be increased without reducing a laser tuning range, thereby allowing use of at least one of a reduced first selected voltage and a reduced second selected voltage.
-
-
19. The laser of claim 1, wherein said frequency selective element comprises:
-
a polarization selective element having a high transmission axis;
a birefringent medium with an ordinary axis and an extraordinary axis oriented at substantially +45° and
−
45°
, respectively, with respect to the high transmission axis of the selective element;
a birefringent electro-optical medium with an ordinary axis and an extraordinary axis oriented at substantially −
45° and
+45°
, respectively, with respect to a high transmission axis of the polyarization selective element; and
voltage means for applying a selected voltage to said electro-optical medium and for varying the selected voltage over a range of values that includes said gain wavelength band.
-
-
20. The laser of claim 19, wherein said electro-optic medium comprises a nematic or smectic liquid crystal.
Specification