A method of performing spectroscopic measurements provides an optical frequency comb, and directs the comb through or at a sample. The optical frequency comb is generated by gain switching a laser diode constructed from Gallium Nitride and related materials. Various techniques are described for manipulating the comb source to achieve desired benefits for spectroscopy.

A system and method for generating optically synthesized microwave signals with broadband tunability is disclosed. The system includes a first laser and a second laser, where the first laser and second laser are optically coupled to each other. The second laser is operable to receive optical signals injected by the first laser, and to output optical signals via one or more feedback paths. The system provides for singular or mutual optical injection. A photodetector is optically coupled to the second laser over the one or more feedback paths, and operable to convert optical signals to electrical signals. A phase modulator is coupled to the photodetector, where the electrical signals from the photodetector are operable to drive the phase modulator and close the one or more feedback paths. The respective lengths of the feedback paths may be selected such that their corresponding lengths provide a frequency spacing for optical signals therein that is significantly smaller than a frequency of microwave signals.

A criterion method of GCCS (Globally Complete Chaos Synchronization) for three-node VCSEL (Vertical Cavity Surface Emitting Laser) networks with delay coupling is provided, including steps of: providing a delay-coupled VCSEL network consisting of three identical units and dynamic equations of the VCSEL network; providing assumptions of an outer-coupling matrix and a unitary matrix under the dynamic equations of the VCSEL network; in the three-node VCSEL network, determining rate equations of i-VCSEL, determining dynamic equations of a synchronization manifold, and determining a master-stability equation; calculating three maximum Lyapunov exponents; determining a stability of a synchronization state of the three-node VCSEL network, and determining whether the synchronization manifold of the VCSEL network is a chaotic waveform. Through a master-stability function, the method for determining whether the GCCS is achieved among all node lasers is provided, which solves a difficult problem of GCCS criterion for the VCSEL networks.

Provided is a laser device according to an embodiment of the inventive concept. The laser device includes: a semiconductor substrate; a germanium single crystal layer on the semiconductor substrate; and a pumping light source disposed on the germanium single crystal layer and configured to emit light toward the germanium single crystal layer, wherein the germanium single crystal layer receives the light to thereby output laser.

A high-power single-frequency laser system and a method for implementing the same. The system and method require only a photodetector (110) and a narrow optical bandpass filter (108) to probe the spectral mode of slave laser (106), no additional bulky devices are required. The photodetector (110) and narrow optical bandpass filter (108) can be easily integrated into the beam path. The spectral mode of slave laser (106) is monitored through the reflected signal from the narrow-laser line filter (108), which is neither sensitive to beam alignment nor bandwidth limited. As a result, high spectral mode purity and low intensity noise of the slave laser (106) can be simultaneously obtained. The slave laser (106) can be locked even when the master laser (102) frequency is dynamically scanned over GHIz range. The system and method can be applied in laser cooling and trapping of atoms towards degenerate dipolar quantum gases.

GaN-based nanowire heterostructures have been intensively studied for applications in light emitting diodes (LEDs), lasers, solar cells and solar fuel devices. Surface charge properties play a dominant role on the device performance and have been addressed within the prior art by use of a relatively thick large bandgap AlGaN shell covering the surfaces of axial InGaN nanowire LED heterostructures has been explored and shown substantial promise in reducing surface recombination leading to improved carrier injection efficiency and output power. However, these lead to increased complexity in device design, growth and fabrication processes thereby reducing yield/performance and increasing costs for devices. Accordingly, there are taught self-organising InGaN/AlGaN core-shell quaternary nanowire heterostructures wherein the In-rich core and Al-rich shell spontaneously form during the growth process.

A laser apparatus is provided, comprising a semiconductor substrate, an active layer disposed on the semiconductor substrate, a folded waveguide disposed on the active layer and forming a resonant structure, the folded waveguide comprising at least two substantially straight waveguide portions coupled by a connecting waveguide structure, with the folded waveguide having a first end and a second end located at one or more edges of the semiconductor substrate, wherein at least one of the ends includes a mirror, and an electrode coupled to the folded waveguide and configured to create photons in the folded waveguide when receiving electrical power. The waveguide emits laser light comprising the photons, with the laser light emitted at an edge of the semiconductor substrate.

A configuration of a DFB laser-based wavelength tunable laser is well known, but long resonators have difficulty in forming uniform resonators due to production variations, thereby inducing limitation in narrowing the spectral linewidth in the DFB laser-based wavelength tunable laser as well. In the semiconductor laser device of the present invention, a semiconductor laser that oscillates in a single mode and a low-loss lightwave circuit using SiO.sub.2 glass are arranged on the common substrate. The lightwave circuit is configured such that part of output light from the semiconductor laser propagates through a certain length of an optical path, and then is reflected by a reflector and is fed back to the semiconductor laser. Output light from the semiconductor laser and an input waveguide of the lightwave circuit can also be configured to be optically connected directly to each other. The present invention can provide a compact laser device with a narrowed spectral linewidth and stable wavelength controllability.

In a semiconductor laser according to an embodiment of the present disclosure, a ridge part has a structure in which a plurality of gain regions and a plurality of Q-switch regions are each disposed alternately with each of separation regions being interposed therebetween in an extending direction of the ridge part. The separation regions each have a separation groove that separates from each other, by a space, the gain region and the Q-switch region adjacent to each other. The separation groove has a bottom surface at a position, in a second semiconductor layer, higher than a part corresponding to a foot of each of both sides of the ridge part. The semiconductor laser includes an electrode provided over the bottom surface of each separation groove with an insulating layer being interposed therebetween.

Provided is a tunable laser source including a plurality of optical waveguides, at least three optical resonators provided between the plurality of optical waveguides and optically coupled to the plurality of optical waveguides, the at least three optical resonators having different lengths, and at least one optical amplifier provided on at least one of the plurality of optical waveguides, wherein a ratio of a first length of a first optical resonator of the at least three optical resonators to a second length of a second optical resonator of the at least three optical resonators is not an integer.