Tunable optical filters having electro-optic whispering-gallery-mode resonators
First Claim
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1. A method for filtering an optical signal, comprising:
- directing an input optical signal into an optical resonator configured to support whispering gallery modes and comprising a portion where the whispering gallery modes are present, wherein at least the portion of the optical resonator exhibits an electro-optical effect;
coupling light out of the optical resonator to produce a filtered optical output from the input optical signal; and
applying an electrical control signal to at least the portion in the optical resonator to tune a spectral transmission peak of the optical resonator and thus to select spectral components in the input optical signal in the filtered optical output.
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Abstract
Tunable optical filters using whispering-gallery-mode (WGM) optical resonators-are described. The WGM optical resonator in a filter exhibits an electro-optical effect and hence is tunable by applying a control electrical signal.
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Citations
32 Claims
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1. A method for filtering an optical signal, comprising:
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directing an input optical signal into an optical resonator configured to support whispering gallery modes and comprising a portion where the whispering gallery modes are present, wherein at least the portion of the optical resonator exhibits an electro-optical effect;
coupling light out of the optical resonator to produce a filtered optical output from the input optical signal; and
applying an electrical control signal to at least the portion in the optical resonator to tune a spectral transmission peak of the optical resonator and thus to select spectral components in the input optical signal in the filtered optical output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A tunable optical filter, comprising:
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an optical resonator configured to support whispering gallery modes and comprising at least a portion where the whispering gallery modes are present, wherein at least the portion of the optical resonator exhibits an electro-optical effect;
at least one electrode formed on the optical resonator to guide an electrical control signal into the optical resonator to spatially overlap with the whispering gallery modes; and
a control unit coupled to the at least one electrode to supply an electrical control signal to the one portion to tune a refractive index and thus a transmission peak of the optical resonator via the electro-optical effect. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A device, comprising a receiver to receive a radiation signal carrying a plurality of signal channels and to extract a selected channel from the received signal channels, wherein the receiver comprises:
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an optical modulator to modulate an optical beam in response to the radiation signal to produce a modulated optical signal carrying the signal channels, a tunable optical filter having (1) an optical resonator which is configured to support whispering gallery modes and comprise at least a portion where the whispering gallery modes are present, wherein at least the portion of the optical resonator exhibits an electro-optical effect, (2) at least one electrode formed on the optical resonator to guide an electrical control signal into the optical resonator to spatially overlap with the whispering gallery modes, and (3) a control unit coupled to the at least one electrode to supply an electrical control signal to the one portion to tune a refractive index and thus a transmission peak of the optical resonator via the electro-optical effect, wherein the optical filter is Located to receive and filter the modulated optical signal to produce a filtered optical output that carries only the selected signal channel, an optical detector to convert the filtered optical output into an electrical signal, and a mixer that mixes the electrical signal with a reference signal to extract the selected signal channel. - View Dependent Claims (18, 19)
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20. A tunable filter, comprising:
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an optical modulator having an input port to receive an input signal at an RF or microwave frequency and responsive to the input signal to modulate a first light beam at an optical carrier frequency to carry the input signal;
a light source to produce a light beam;
an optical splitter to split the light beam into the first light beam directed through the optical modulator and a second light beam directed through a separate optical path;
an optical resonator positioned to receive and filter the modulated light from the optical modulator to produce a filtered optical output, the optical resonator supporting whispering gallery modes and comprising a portion where the whispering gallery modes are present, wherein at least the portion of the optical resonator exhibits an electro-optical effect;
a resonator control unit to supply an electrical control signal to at least the portion in the optical resonator to tune a spectral transmission peak of the optical resonator and thus to select one or more spectral components in the input optical signal in the filtered optical output;
an optical combiner to combine the filtered optical output and the second light beam to produce a combined optical signal; and
an optical detector to convert the combined optical signal into an output signal which carries the selected one or more spectral components. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A method for filtering an input signal at an RF or microwave frequency to produce a filtered output signal, comprising:
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deriving first and second optical beams from a CW light beam;
directing the first optical beam through art optical modulator to produce a modulated optical beam;
applying the input signal to control the optical modulator in modulating the first optical beam to carry the input signal in the modulated optical beam;
directing the second optical beam through at separate optical path;
directing the modulated optical beam through a tunable optical resonator to produce a filtered optical beam, the tunable optical resonator supporting whispering gallery modes and changing a spectral transmission via an electro-optical effect in response to an electrical control signal;
applying the electrical control signal to the optical resonator to tune a spectral transmission peak of the optical resonator and thus to select one or more spectral components in the input optical signal in the filtered optical beam;
combining the filtered optical beam and the second optical beam to produce a combined optical signal; and
using a photodetector to convert the combined optical signal into the filtered output signal which carries the selected one or more spectral components. - View Dependent Claims (32)
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Specification