Methods, systems, and apparatus, for optical communication. One apparatus includes a Fabry-Perot (FP) laser diode assembly coupled to a first port of a circulator; an optical amplifier coupled to a second port of the circulator; a wavelength division multiplexer (WDM) filter coupled to a third port of the circulator; and a Faraday rotator mirror coupled to the WDM filter.

It is necessary to reduce the power consumption of a plurality of optical amplifiers when there is a difference in the required pumping power between the plurality of optical amplifiers; therefore, an optical amplifying apparatus according to an exemplary aspect of the invention includes a plurality of optical amplifying means for amplifying a plurality of optical signals, each of the plurality of optical amplifying means including a gain medium; a plurality of laser light generating means for generating a plurality of laser beams; at least one optical coupling means for coupling the plurality of laser beams variably in accordance with a coupling factor and outputting a plurality of excitation light beams, each of the plurality of excitation light beams exciting the gain medium; and controlling means for controlling the coupling factor and an output power of each of the plurality of laser light generating means.

A semiconductor optical amplifier array device includes: a substrate; and a plurality of semiconductor optical amplifiers formed on the substrate, each of the semiconductor optical amplifiers including an active region, and two input-output ports optically connected to the active region and disposed on same facet of the semiconductor optical amplifier array device. The plurality of semiconductor optical amplifiers include a first semiconductor optical amplifier in which length of the active region is equal to a first length, and a second semiconductor optical amplifier in which length of the active region is equal to a second length that is different from the first length.

A tunable laser device based on silicon photonics includes a substrate configured with a patterned region comprising one or more vertical stoppers, an edge stopper facing a first direction, a first alignment feature structure formed in the patterned region along the first direction, and a bond pad disposed between the vertical stoppers. Additionally, the tunable laser includes an integrated coupler built in the substrate located at the edge stopper and a laser diode chip including a gain region covered by a P-type electrode and a second alignment feature structure formed beyond the P-type electrode. The laser diode chip is flipped to rest against the one or more vertical stoppers with the P-type electrode attached to the bond pad and the gain region coupled to the integrated coupler. Moreover, the tunable laser includes a tuning filter fabricated in the substrate and coupled via a wire waveguide to the integrated coupler.

A method for increasing the MeV hot electron yield and secondary radiation produced by short-pulse laser-target interactions with an appropriately high or low atomic number (Z) target. Secondary radiation, such as MeV x-rays, gamma-rays, protons, ions, neutrons, positrons and electromagnetic radiation in the microwave to sub-mm region, can be used, e.g., for the flash radiography of dense objects.

A tunable laser for a transceiver includes a silicon photonics substrate, first and second patterned regions each being defined in the substrate a step lower than a flat surface region of the substrate, first and second laser diode chips arranged in the first and second patterned regions, the patterned regions being configured to align the gain regions of the first and second laser diode chips with integrated couplers formed in the substrate adjacent to the first and second patterned regions to facilitate flip-bonding the first and second laser diode chips within the patterned regions, and a tuning filter coupled to the first laser diode chip and the second laser diode chip via the integrated couplers. The tuning filter is configured to receive laser light from each of the first and second laser diode chips and generate a laser output having a gain determined by each of the gain regions.

A room-temperature semiconductor maser, including a first matching network, a second matching network, a heterojunction-containing transistor, and a resonant network. The output end of the first matching network is connected to the drain of the heterojunction-containing transistor. The input end of the second matching network is connected to the source of the heterojunction-containing transistor. The gate of the heterojunction-containing transistor is connected to the resonant network. The pumped microwaves are fed into the input end of the first matching network.

Embodiments of the invention describe polarization insensitive optical devices utilizing polarization sensitive components. Light comprising at least one polarization state is received, and embodiments of the invention select a first optical path for light comprising a first polarization state or a second optical path for light comprising a second polarization state orthogonal to the first polarization state. The optical paths include components to at least amplify and/or modulate light comprising the first polarization state; the second optical path includes a polarization rotator to rotate light comprising the second polarization state to the first polarization state. Embodiments of the invention further describe optical devices including a polarization mode converter to convert light comprising a first and a second polarization state to light comprising different spatial modes of the first polarization state; light comprising the different spatial modes of the first polarization state is subsequently amplified and modulated.

A tunable laser for a transceiver includes a silicon photonics substrate, first and second patterned regions each being defined in the substrate a step lower than a flat surface region of the substrate, first and second laser diode chips arranged in the first and second patterned regions, the patterned regions being configured to align the gain regions of the first and second laser diode chips with integrated couplers formed in the substrate adjacent to the first and second patterned regions to facilitate flip-bonding the first and second laser diode chips within the patterned regions, and a tuning filter coupled to the first laser diode chip and the second laser diode chip via the integrated couplers. The tuning filter is configured to receive laser light from each of the first and second laser diode chips and generate a laser output having a gain determined by each of the gain regions.

A semiconductor optical amplifier includes: a substrate; a light source unit that is formed on the substrate; and an optical amplification unit that includes a conductive region extending, from the light source unit, in a predetermined direction along a surface of the substrate, and a nonconductive region around the conductive region. The optical amplification unit amplifies propagation light that propagates, from the light source unit, in the predetermined direction as slow light, and emits the propagation light that is amplified in an emission direction that intersects with the surface. The maximum optical power of the propagation light is larger than the maximum optical power in a vertical oscillation mode.