Channel-switched tunable laser for DWDM communications
First Claim
1. A laser apparatus comprising:
- an amplifying waveguide segment capable of providing optical gain over a first optical frequency band, said amplifying waveguide segment characterized by a first temperature dependent effective refractive index with a positive refractive index change with increases of temperature;
a passive intracavity waveguide segment optically coupled to said amplifying waveguide segment for providing a path for optical energy therein, said passive intracavity waveguide segment characterized by a second temperature-dependent effective refractive index with a negative refractive index change with increases of temperature; and
a frequency selective feedback structure coupling optical energy of a selected second optical frequency band within said first optical frequency band back into said amplifying waveguide segment forming a resonant cavity, wherein said frequency selective feedback structure comprises a thermo-optical feedback waveguide segment, a grating formed in said feedback waveguide segment, and a thermal actuator for heating said feedback waveguide segment to produce a change in refractive index of said feedback waveguide segment for tuning said selected second optical frequency band, and wherein a round trip optical path traversed by said optical energy within said resonant cavity between successive couplings into said amplifying waveguide segment has a round trip optical length that is substantially independent of ambient temperature over a specified ambient temperature range.
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Abstract
Laser source including materials with negative index of refraction dependence on temperature and with temperature independent coincidence between cavity modes and a set of specified frequencies such as DWDM channels in telecommunications applications. The free spectral range may be adjusted to equal a rational fraction of the specified frequency interval. The operating frequency may be defined by a frequency selective feedback element that is thermo-optically tuned by the application of heat from an actuator without substantially tuning the cavity modes. The operating frequency may be induced to hop digitally between the specified frequencies. In a particular embodiment, semiconductor amplifier and polymer waveguide segments form a linear resonator with a thermo-optically tuned grating reflector. In a further embodiment, an amplifier and two waveguides from a tunable grating assisted coupler form a ring resonator. Tuning may also be accomplished by means of applying an electric field across a liquid crystal portion of the waveguide structure within the grating.
102 Citations
31 Claims
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1. A laser apparatus comprising:
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an amplifying waveguide segment capable of providing optical gain over a first optical frequency band, said amplifying waveguide segment characterized by a first temperature dependent effective refractive index with a positive refractive index change with increases of temperature;
a passive intracavity waveguide segment optically coupled to said amplifying waveguide segment for providing a path for optical energy therein, said passive intracavity waveguide segment characterized by a second temperature-dependent effective refractive index with a negative refractive index change with increases of temperature; and
a frequency selective feedback structure coupling optical energy of a selected second optical frequency band within said first optical frequency band back into said amplifying waveguide segment forming a resonant cavity, wherein said frequency selective feedback structure comprises a thermo-optical feedback waveguide segment, a grating formed in said feedback waveguide segment, and a thermal actuator for heating said feedback waveguide segment to produce a change in refractive index of said feedback waveguide segment for tuning said selected second optical frequency band, and wherein a round trip optical path traversed by said optical energy within said resonant cavity between successive couplings into said amplifying waveguide segment has a round trip optical length that is substantially independent of ambient temperature over a specified ambient temperature range. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A laser apparatus comprising:
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an amplifying waveguide segment capable of providing optical gain over a first optical frequency band, said amplifying waveguide segment characterized by a first temperature dependent effective refractive index with a positive refractive index change with increases of temperature;
a passive intracavity waveguide segment optically coupled to said amplifying waveguide segment for providing a path for optical energy therein, said passive intracavity waveguide segment characterized by a second temperature-dependent effective refractive index with a negative refractive index change with increases of temperature; and
a frequency selective feedback structure coupling optical energy of a selected second optical frequency band within said first optical frequency band from said amplifying waveguide segment back into said amplifying waveguide segment forming a resonant cavity, wherein a round trip optical path traversed by said optical energy within said resonant cavity between successive couplings into said amplifying waveguide segment has a round trip optical length that is independent of ambient temperature over a specified ambient temperature range, wherein said round trip optical length defines a free spectral range of said resonant cavity that is a rational fraction of a specified frequency channel spacing over a portion of said first optical frequency band. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A laser communication device comprising:
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a light amplifying medium capable of providing optical gain over a first optical frequency band extending over an optical communications frequency band;
optical feedback means, including a frequency selective structure capable of providing optical feedback to said light amplifying medium of a selected second optical frequency within said first optical frequency band, for defining a resonant cavity including said light amplifying medium said resonant cavity having an effective round trip optical length characterizing a round trip optical path of optical energy within said resonant cavity between successive couplings of said optical energy into said light amplifying medium said effective round trip optical path length of said resonant cavity establishing longitudinal mode frequencies, a subset of said longitudinal mode frequencies coinciding with specified communications channels within said optical communications frequency band; and
an intracavity medium optically coupled to said light amplifying medium in said round trip optical path of optical energy within said resonant cavity, said intracavity medium characterized by a negative refractive index change with increases in temperature and having a length chosen such that said effective round trip optical length is substantially independent of temperature over a specified temperature range. - View Dependent Claims (17, 18, 19, 20, 21, 22)
a thermal actuator for heating said feedback element to produce a change in refractive index of said feedback element for tuning said selected second optical frequency to a specified communication channel frequency. -
19. The device of claim 17 wherein said selected second optical frequency of said frequency selective structure is substantially independent of temperature.
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20. The laser apparatus of claim 19 wherein said frequency selective structure comprises an electro-optical feedback element, and
an electrode actuator for applying an electric field in said feedback element to produce a change in refractive index of said feedback element for tuning said selected second optical frequency to a specified communication channel frequency. -
21. The device of claim 17 wherein said grating structure is formed on a second waveguide segment coupled to said optical path in s aid cavity.
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22. The device of claim 16 wherein said resonant cavity is a ring resonator.
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23. A laser apparatus comprising:
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an amplifying waveguide segment capable of providing optical gain over a first optical frequency band, said amplifying waveguide segment characterized by a first temperature dependent effective refractive index with a positive refractive index change with increases of temperature;
first and second intracavity waveguide segments optically coupled to opposite ends of said amplifying waveguide segment for providing a path for optical energy therein, at least one of said passive intracavity waveguide segments characterized by a second temperature-dependent effective refractive index with a negative refractive index change with increases of temperature; and
a frequency selective feedback structure coupling optical energy of a selected second optical frequency band within said first optical frequency band between said first and second passive intracavity waveguide segments forming a ring resonant cavity, wherein a round trip optical path traversed by said optical energy within said ring resonant cavity between successive couplings into said amplifying waveguide segment has a round trip optical length that is substantially independent of ambient temperature over a specified ambient temperature range, wherein said round trip optical length defines a free spectral range of said resonant cavity that is a rational fraction of a specified communication frequency channel spacing over a portion of said first optical frequency band. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31)
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Specification