Back scattering in an optical waveguide at an operating wavelength is controlled by adjusting an optical phase of light propagating in the waveguide at one or more locations along the waveguide. A portion of the back scattered light is tapped off near an input port and coupled into a photodetector. A controller detects changes in the photodetector signal and adjusts an optical phase tuner configured to control the optical phase of light in the waveguide at the selected location or locations. The optical phase tuner may be configured to vary the refractive index of at least a portion of the waveguide.

A method may comprise: generating an optical frequency comb; applying a filter in a first configuration to the generated optical frequency comb to select a first frequency of the optical frequency comb, wherein, in the first configuration, the first frequency aligns with a first pass-band of the filter, and a second frequency of the optical frequency comb does not align with a second pass-band of the filter; altering the filter to a second configuration to shift the first pass-band and the second pass-band to a shifted first pass-band and a shifted second pass-band; and applying the altered filter to the generated optical frequency comb to select the second frequency of the optical frequency comb, wherein the second frequency aligns with the shifted second pass-band of the filter, and the first frequency of the optical frequency comb does not align with the shifted first pass-band of the filter.

An optical module has an optical amplifier that amplifies an optical signal in which multiple wavelengths are multiplexed, an optical demultiplexer that separates the multiple wavelengths from the optical signal having been amplified by the optical amplifier, a first photodetector that monitors the optical signal at an input side of the optical amplifier, a second photodetector that monitors each of the multiple wavelengths at an output side of the optical demultiplexer, and a control circuit that controls a center wavelength of a filter of the optical demultiplexer based upon a first output from the first photodetector and a second output from the second photodetector.

A method and a system for pulsed excitation of a nonlinear medium for photon pair generation, he method comprising exciting a single narrow resonance of a nonlinear resonant element with a pulsed laser field, comprising embedding a nonlinear resonant element directly into an external laser cavity and locking the cavity modes.

One feature pertains to an apparatus that includes apparatus that includes an evanescent field coupler having a first surface that evanescently couples light between the evanescent field coupler and an open dielectric resonator. The apparatus also includes a thin film coating covering at least a portion of the first surface of the evanescent field coupler. The thin film coating is specifically designed so that the thin film coating reflects light of a first wavelength.

A method for producing an organic microdisk structure 40, which is characterized by comprising: a cladding layer formation step 1 wherein a cladding layer 12 is formed by printing a first ink 11 that contains a fluorine-containing hyperbranched polymer on a substrate 10 by an inkjet method; a core layer formation step 2 wherein a core layer 22 is formed by printing a second ink 21 that contains a laser dye and a triazine-based hyperbranched polymer containing no fluorine on the cladding layer 12 by an inkjet method; and an etching step 3 wherein the cladding layer 12 is etched using a solvent 31 that dissolves only the fluorine-containing hyperbranched polymer. Consequently, an unconventional novel method for producing an organic microdisk structure with use of an inkjet method is able to be provided.

A method may comprise: generating an optical frequency comb; applying a filter in a first configuration to the generated optical frequency comb to select a first frequency of the optical frequency comb, wherein, in the first configuration, the first frequency aligns with a first pass-band of the filter, and a second frequency of the optical frequency comb does not align with a second pass-band of the filter; altering the filter to a second configuration to shift the first pass-band and the second pass-band to a shifted first pass-band and a shifted second pass-band; and applying the altered filter to the generated optical frequency comb to select the second frequency of the optical frequency comb, wherein the second frequency aligns with the shifted second pass-band of the filter, and the first frequency of the optical frequency comb does not align with the shifted first pass-band of the filter.

An optical system can automatically lock an adjustable spectral filter to a first wavelength of an incoming light signal, and can automatically filter an additional incoming light signal at the first wavelength. A tunable filter can have a filtering spectrum with an adjustable peak wavelength and increasing attenuation at wavelengths away from the adjustable peak wavelength. The tunable filter can receive first input light, having a first wavelength, and can spectrally filter the first input light to form first output light. A detector can detect at least a fraction of the first output light. Circuitry coupled to the detector and the tunable filter can tune the tunable filter to maximize a signal from the detector and thereby adjust the peak wavelength to match the first wavelength. The tunable filter further can receive second input light and spectrally filter the second input light at the first wavelength.

An optical waveguide element includes: a cladding portion made of silica-based glass; and a plurality of optical waveguides positioned in the cladding portion and made of silica-based glass in which ZrO.sub.2 crystal particles are dispersed. The optical waveguide element is a planar lightwave circuit. The plurality of optical waveguides configure an arrayed waveguide grating element.

An optical device includes: a first port group P including n ports P.sub.i; a second port Q; and a wavelength multiplexer/demultiplexer disposed between the first port group P and the second port Q. In a case where light beams L.sub.i of predetermined different n wavelengths .sub.i corresponding to the respective ports P.sub.i are inputted to the wavelength multiplexer/demultiplexer, the wavelength multiplexer/demultiplexer combines the light beams L.sub.i into light L and outputs the light L to the second port Q. In a case where light L is inputted to the second port Q, the wavelength multiplexer/demultiplexer separates the light L into light beams L.sub.i of the wavelengths .sub.i and outputs the light beams L.sub.i to the corresponding ports P.sub.i.