Apparatus and methods for altering one or more spectral, spatial, or temporal characteristics of a light-emitting device are disclosed. Generally, such apparatus may include a volume Bragg grating (VBG) element that receives input light generated by a light-emitting device, conditions one or more characteristics of the input light, and causes the light-emitting device to generate light having the one or more characteristics of the conditioned light.

A bidirectional mode-locked fiber laser includes first and second passive optical fibers, a doped optical fiber, first and second polarization controllers, and first and second polarized beamsplitters that are arranged as a ring cavity with clockwise (CW) and counter-clockwise (CCW) directions. The laser imparts different nonlinear phase shifts in the CW and CCW directions, corresponding to CW and CCW repetition rates that are slightly different. When the normalized difference in repetition rates is less than approximately 10.sup.−5, both directions can be mode-locked simultaneously, thereby preventing one direction from inhibiting mode-locking of the other direction. Optical-fiber nonlinearity implements an intra-cavity bidirectional artificial saturable absorber based on nonlinear polarization rotation. The laser uses only components with normal group-velocity dispersion (GVD), thereby achieving higher pulse energies than mode-locked lasers utilizing negative GVD. The combination of artificial saturable absorber and normal GVD components increases pulse energy, which improves the efficiency of spectral broadening.

A single-laser light source system for cold atom interferometers, comprising: a reference light module including a narrow-bandwidth laser and a frequency stabilization module and an optical frequency shift module including a first electro-optic modulator and a first narrow-bandwidth optical-fiber filter. The first electro-optic modulator is connected to the first narrow-bandwidth optical-fiber filter by an optical fiber, and the first electro-optic modulator is connected to the laser by an optical fiber. The first electro-optic modulator receives an initial light from the laser, modulates the initial light by a modulation signal with a preset frequency, and generates sidebands with the preset frequency. The first narrow-bandwidth optical-fiber filter filters the optical signal at the output of the first electro-optic modulator to obtain a frequency-shifted light as the +1-order sideband. The frequency-shifted light is used for modulation to obtain a measurement and control light of the cold atom interferometer.

An amplified optical link having a fault-protection capability that is based, at least in part, on the ability to selectively and independently power up and down different groups of optical amplifiers within the link. In an example embodiment, the optical link is implemented using an optical fiber cable having an electrical power line and arrays of optical amplifiers connected between successive optical fiber segments to form a plurality of disjoint groups of parallel optical paths between the ends of the optical fiber cable. The electrical power line is operable to selectively power, as a group, the optical amplifiers of at least some of the disjoint groups. In various embodiments, different optical paths can be implemented using different respective strands of a single-core optical fiber, different respective cores of a multi-core optical fiber, and/or different respective sets of spatial modes of a multimode optical fiber.

A laser module includes a gain chip, temperature sensors, a case, and a thermoelectric cooler (TEC). The gain chip emits a laser beam. One of the temperature sensors measures a first temperature of the gain chip and is encompassed by the gain chip. The other temperature sensor is adhered to the case and measures a second temperature. The TEC tunes the laser beam emitted by the gain chip to a desired wavelength by varying the first temperature of the gain chip through a set of third temperatures for various values of the second temperature. The set of third temperatures is selected from various values of the first temperature such that the laser beam emitted at the set of third temperatures is mode-hop free.

A bidirectional mode-locked fiber laser includes first and second passive optical fibers, a doped optical fiber, first and second polarization controllers, and first and second polarized beamsplitters that are arranged as a ring cavity with clockwise (CW) and counter-clockwise (CCW) directions. The laser imparts different nonlinear phase shifts in the CW and CCW directions, corresponding to CW and CCW repetition rates that are slightly different. When the normalized difference in repetition rates is less than approximately 10.sup.−5, both directions can be mode-locked simultaneously, thereby preventing one direction from inhibiting mode-locking of the other direction. Optical-fiber nonlinearity implements an intra-cavity bidirectional artificial saturable absorber based on nonlinear polarization rotation. The laser uses only components with normal group-velocity dispersion (GVD), thereby achieving higher pulse energies than mode-locked lasers utilizing negative GVD. The combination of artificial saturable absorber and normal GVD components increases pulse energy, which improves the efficiency of spectral broadening.

Systems and methods for temporal amplitude modulation of an optical beam. An exemplary system may include a birefringent fiber positioned between two polarizers, or between a polarized input light source and an output polarizer. Light may enter the birefringent fiber as linearly polarized. Depending on birefringence and orientation of the birefringent fiber, the polarization state changes as the light propagates through the birefringent fiber. This changed polarization state then enters the output polarizer, for which transmission is a function of the polarization state and the relative orientation of the polarization axis. The polarization state emerging from the birefringent fiber may be changed by modulating the fiber birefringence, for example through application of an external stress. Net transmittance of the system may be varied according to a magnitude of an external force (e.g., pressure) to some or all of the birefringent fiber.

A gain mirror is created for use as an optical amplifier in a solid state ring laser rotation sensor. Such a ring laser includes at least three mirrors for reflecting counter propagating laser beams around a closed loop optical path, wherein at least one of the mirrors is a gain mirror. The gain mirror is formed by applying a thin film of silica, a few half wavelengths thick and doped with Nd isotopes, onto a very high reflectivity mirror and then using a laser diode to pump it with intense light to form a population inversion in Nd.sup.3+ ions. An assembly consisting of this gain mirror and a pump laser diode can be used as an optical amplifier in a solid state ring laser to generate the two counter propagating laser light beams needed to measure rotation.

A pulsed fiber generator is configured with a unidirectional ring waveguide configured to emit a train of pulses. The ring waveguide includes multiple fiber amplifiers, chirping fiber components coupled to respective outputs of first and second fiber amplifiers, and multiple spectral filters coupled to respective outputs of the chirping components. The filters have respective spectral band passes centered around different central wavelengths so as to provide leakage of light along the ring cavity in response to nonlinear processes induced in the ring cavity. The pulse generator operates at a preliminary stage during which it is configured to develop a pitch to a signal, and at a steady stage during which it is configured to output a train of pulses through an output coupler at most once per a single round trip of the signal.

Systems and apparatuses for a polarization laser sensor are disclosed. The polarization laser sensor can include a pump source, a common section, a reference section and a detection section. The common section is provided with a gain medium, and the detection section is provided with a sensing element configured to cause an optical path difference. The reference section and the detection section are connected to the common section though a first polarization splitting unit and a second polarization splitting unit. The common section is provided with an output unit or each of the reference section and the detection is provided with the output unit, the output unit is connected to a photoelectric detector through a light uniting unit, and a polarization rotation unit is disposed between the light uniting unit and the output unit.