A low-noise amplifier includes a gain medium and two or more amplifier stages. Each amplifier stage includes an optical filter to pass all wavelengths of a respective input optical signal in a given propagation direction over the gain medium and reflect wavelengths above a respective threshold wavelength received in the opposite direction, and a respective Raman pump to inject a pump light centered at a wavelength lower than the threshold wavelength onto the gain medium for transmission in the given direction. A first amplifier stage outputs a first combined optical signal including all wavelengths of the respective input optical signal and a pump light injected by the respective Raman pump. The second amplifier stage receives the first combined optical signal as its input and outputs a second combined optical signal including all wavelengths of the first combined optical signal and a pump light injected by the respective Raman pump.

A micro disk laser having a greater strength of oscillation in one direction than in another direction and unidirectionally oscillating includes a micro disk having an oval shape corresponding to a modified ellipse obtained by changing a length of a short axis of an ellipse according to a position of a long axis while lengths of first and second side portions of the long axis are fixed in the ellipse, the ellipse having the long axis and the short axis having a different length than the long axis.

A quantum dot comb laser includes a body defining a lasing cavity and an extension defining an external cavity, the FSR of the lasing cavity being an inverse of an integer multiple of the FSR of the external cavity.

An apparatus for emitting pulsed electromagnetic laser radiation includes a laser gain element; an optical arrangement defining a laser resonator and arranged to re-direct radiation emitted by the gain element along a beam path back onto the gain element, the optical arrangement comprising an output coupler configured to couple a portion of the radiation in the laser resonator out of the laser resonator; and, a pump arrangement configured to pump the laser gain element. The optical arrangement includes a mode locker placed in the laser resonator in the beam path, and a birefringent element placed in the laser resonator in the beam path.

A resonator is provided having a waveguide with a first boundary, a second boundary parallel to the first boundary, a first end, a second end, and a waveguide cavity at least partly between the first boundary and the second boundary. A first grating, having a period of distance a, is at the first boundary of the waveguide, and a second grating, having a period of distance a, is at the second boundary of the waveguide. The first and second boundaries are separated by a constant distance d. The first boundary may have a periodic profile aligned with a periodic profile of the second boundary. The periodic profile of the first boundary and the second boundary may be a sinusoidal profile, a square profile, or profile of another shape. The resonator may be suitable for use in a distributed feedback laser.

A laser oscillator includes: a plurality of laser media to emit laser beams having different wavelengths; a diffraction grating to emit, in a superimposed state, the laser beams incident from the laser media; a partially reflective element to reflect part of the laser beams emitted from the diffraction grating and return the part of the laser beams to the diffraction grating, and to transmit a remainder; and a plurality of lenses each disposed between a corresponding one of the laser media and the diffraction grating. The lenses are each disposed in an optical path formed between a corresponding one of the laser media and the diffraction grating, and the lenses superimpose the laser beams from the laser media on an incident surface of the diffraction grating such that the laser beams have an equal outer diameter.

A surface-emitting quantum cascade laser of an embodiment comprises a substrate, an active layer, and a photonic crystal layer. The active layer has optical nonlinearity, and is capable of emitting a first and a second infrared laser light. The photonic crystal layer includes a first and a second region. The rectangular grating of the first region is orthogonal to the rectangular grating of the second region. The first infrared laser light has a wavelength corresponding to a maximum gain outside a first photonic bandgap in a direction parallel to a first side of two sides constituting the rectangular grating. The second infrared laser light has a wavelength corresponding to a maximum gain outside a second photonic bandgap in a direction parallel to a second side of the two sides of the rectangular grating.

In an embodiment a semiconductor emitter includes a semiconductor layer sequence having a plurality of active zones, each active zone including at least one quantum well layer and at least two barrier layers between which the at least one quantum well layer is embedded, and at least one tunnel diode located along a growth direction of the semiconductor layer sequence between adjacent active zones, wherein a thickness of the at least one tunnel diode is at most 40 nm, and wherein a distance between adjacent barrier layers of adjacent active zones, facing the at least one tunnel diode, is at most 50 nm.

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 tunable laser including: an optical cavity including a first and second end mirrors, and a center mirror; a quantum well gain region between the end mirrors; and a transparent heat spreader bonded to the quantum well gain region; wherein the optical cavity is configured to generate resonant laser radiation between the end mirrors; the quantum well gain region includes at least one quantum well that is substantially aligned with an antinode of the resonant laser radiation and is located at a fixed distance to the center mirror; the distance from the first end mirror to the center mirror is optimized to maintain maximum output power, and the distance from the second end mirror to the center mirror is adjustable for tuning the laser to a desired output wavelength; the center mirror maintains an antinode of the resonant radiation at a fixed phase relationship with the center mirror.