Waveguide Bragg gratings, optical reflectors and lasers including optical reflectors are disclosed. The optical reflectors include a waveguide, perturbations proximate to the waveguide to create a Bragg grating in the waveguide, and a DC index control structure positioned to vary the DC index along at least a portion of the Bragg grating. In laser embodiments, the waveguide may be coupled to the second end of a semiconductor gain element to form an external cavity having an optical length and a cavity phase. The gain element and optical reflector may be monolithically integrated on a substrate or separate structures.

According to an aspect, an optical system includes a laser diode configured to emit optical signals and at least two size-switchable broken racetrack ring resonators optically coupled to an optical waveguide, where each broken racetrack ring resonator is configured to exhibit a resonant wavelength. The optical system also includes a tuning arrangement associated with the broken racetrack ring resonators, where the tuning arrangement includes a micro electro-mechanical system (MEMS) or nano electro-mechanical system (NEMS) actuator mechanically coupled to a first portion of a first one of the broken racetrack ring resonators and configured to mechanically move the first portion so as to change the resonant wavelength of the first one of the broken racetrack ring resonators.

A multimode laser that generates laser emissions that are transmitted into an optical coupling then an optical filter to test for failures or faults within that optical filter is provided herein. Multimode lasers generate emissions which many different modes are present in the gain curve. Due to this, typical multi-mode laser failure-cases can be observed in the output frequency signal of laser emissions passing through an optical component. By using a spectrometer to analyze the exiting laser wavelengths, specific failure-cases of the optical component can be identified and related to root causes.

A novel narrow linewidth laser device is disclosed that includes a gain element, such as a quantum well, quantum dot or bulk waveguide laser chip and a fiber Bragg grating formed in an optical fiber positioned to receive the output from a first end of the gain element and return a portion of said output back into the gain element. The fiber Bragg grating is constructed so that its power reflectivity profile has a ratio of reflectivity slope over reflectivity at the 3 dB point below the reflectivity peak on the red side (longer wavelength side) of the grating larger than a value of 2/nm. The operating wavelength of the device may be tuned thermally, electrically, or thermo-electrically to be on the red side of the fiber Bragg grating reflectivity profile, preferably, but not necessarily, at the 3 dB point below the reflectivity peak or lower. In another embodiment, a second grating is optically coupled to a second end of the gain element and has a reflectivity profile that overlaps at least a portion of the reflectivity profile of the front end fiber Bragg grating.

A low noise, single mode laser includes a semiconductor gain element generating light and having a highly reflective first end forming a first end of a laser cavity. The gain element may be monolithically or discretely integrated with, or distinct from, and coupled to a waveguide comprised of a low loss material with a refractive index ‘n’ greater than 3. The waveguide includes a Bragg grating forming the second end of the laser cavity. A cavity phase control section may be provided between the gain element and the Bragg grating. Two photodetector monitors provide a feedback signal for locking the light from the gain element to a specific wavelength on the Bragg grating reflection spectrum by varying at least one of the cavity phase control section and the gain element bias current. The Bragg grating may have a physical length larger than 10 mm and that occupies at least 50% of the optical length of the external cavity.

Provided is an external cavity laser (ECL) including a vertical cavity surface emitting laser (VCSEL)-Distributed Bragg Reflector (DBR) type light emitting unit configured to receive a current and emit light, and including a DBR function layer and an active layer for a quantum well formed on one side of this DBR function layer, and an optical circuit unit including a light guide in which one end surface is installed to face an active layer at one side of the active layer, light generated from the active layer is received and guided, and an optical axis is formed vertically to an active layer plane, a reflection pattern that is formed at one side of the light guide so as to receive light output from the other end of the light guide to reflect the light again to the light guide, and an external layer for surrounding the light guide and the reflection pattern, wherein the VCSEL-DBR type light emitting unit and the optical circuit unit are mutually coupled to each other. An optical coupling efficiency in the ECL may be raised by improving an inefficient optical coupling issue including alignment, reflection, and the like in a coupling part of a gain element and a silicon waveguide.

A low noise, single mode laser includes a semiconductor gain element generating light and having a highly reflective first end forming a first end of a laser cavity. The gain element may be monolithically or discretely integrated with, or distinct from, and coupled to a waveguide comprised of a low loss material with a refractive index n greater than 3. The waveguide includes a Bragg grating forming the second end of the laser cavity. A cavity phase control section may be provided between the gain element and the Bragg grating. Two photodetector monitors provide a feedback signal for locking the light from the gain element to a specific wavelength on the Bragg grating reflection spectrum by varying at least one of the cavity phase control section and the gain element bias current. The Bragg grating may have a physical length larger than 10 mm and that occupies at least 50% of the optical length of the external cavity.

Provided is an external cavity laser (ECL) including a vertical cavity surface emitting laser (VCSEL)-Distributed Bragg Reflector (DBR) type light emitting unit configured to receive a current and emit light, and including a DBR function layer and an active layer for a quantum well formed on one side of this DBR function layer, and an optical circuit unit including a light guide in which one end surface is installed to face an active layer at one side of the active layer, light generated from the active layer is received and guided, and an optical axis is formed vertically to an active layer plane, a reflection pattern that is formed at one side of the light guide so as to receive light output from the other end of the light guide to reflect the light again to the light guide, and an external layer for surrounding the light guide and the reflection pattern, wherein the VCSEL-DBR type light emitting unit and the optical circuit unit are mutually coupled to each other.

According to the present invention, an optical coupling efficiency in the ECL may be raised by improving an inefficient optical coupling issue including alignment, reflection, and the like in a coupling part of a gain element and a silicon waveguide.

A method of providing a fiber Bragg grating (FBG) within a laser diode package is proposed that includes first inserting the fiber into the package (typically a stripped end termination of the optical fiber) and aligning the fiber with the laser diode. Once aligned, an external FBG writing system is used to illuminate a selected section of the fiber in place in the package (the package remaining open at this time) in a manner that creates the specific grating line pattern for a particular FBG. When using a UV-based system with a phase mask, a focusing lens is disposed between the phase and the open package to direct the interfering beams into the core region of the stripped fiber. A high-power femtosecond laser source may be used in an alternative arrangement to directly write the structure and form the in-package FBG.

Methods and apparatus for spectral narrowing and wavelength stabilization of broad-area lasers, such as an apparatus including a broad-area laser source configured to emit light along an emission axis in an emission pattern extending along the emission axis, and a single-mode fiber Bragg grating, such as a single-mode core incorporating a fiber Bragg grating embedded in a core of a dual-clad fiber, the single-mode fiber Bragg grating configured to spectrally selectively reflect back light from a sub-aperture portion of the emitted light to the broad-area laser source. The single mode core having the FBG is off-axis in comparison to the central axis of the double-clad fiber and allows for frequency stabilization of the broad area laser diode output improving its performance as pump laser for a doped fiber amplifier.