Abstract: Random number generators include a thermal optical source and detector configured to produce random numbers based on quantum-optical intensity fluctuations. An optical flux is detected, and signals proportional to optical intensity and a delayed optical intensity are combined. The combined signals can be electrical signals or optical signals, and the optical source is selected so as to have low coherence over a predetermined range of delay times. Balanced optical detectors can be used to reduce common mode noise, and in some examples, the optical flux is directed to only one of a pair of balanced detectors.

Abstract: Random number generators include a thermal optical source and detector configured to produce random numbers based on quantum-optical intensity fluctuations. An optical flux is detected, and signals proportional to optical intensity and a delayed optical intensity are combined. The combined signals can be electrical signals or optical signals, and the optical source is selected so as to have low coherence over a predetermined range of delay times. Balanced optical detectors can be used to reduce common mode noise, and in some examples, the optical flux is directed to only one of a pair of balanced detectors.

Abstract: A distributed feedback (DFB) laser includes a substrate of a compound semiconductor material, and quantum-well (QW) active layer(s) overlying the substrate. A p-doped cladding layer including the compound semiconductor material is on one side of the active layer and an n-doped cladding layer is on the other side. A grating is in one of the cladding layers configured to select an operating wavelength for the DFB laser. A waveguide structure in the n-doped cladding layer includes a waveguide layer of a first composition compositionally different from the compound semiconductor material having an optical thickness of 0.7 to 1.5 of the guided wavelength. The waveguide structure can further include a hetero-waveguide stack including a plurality of alternating compositional layers beyond the waveguide layer each having a thickness between one quarter and one half the guided wavelength alternating the compound semiconductor material with a second composition defining a composition wavelength.

Abstract: A distributed feedback (DFB) laser includes a substrate of a compound semiconductor material, and quantum-well (QW) active layer(s) overlying the substrate. A p-doped cladding layer including the compound semiconductor material is on one side of the active layer and an n-doped cladding layer is on the other side. A grating is in one of the cladding layers configured to select an operating wavelength for the DFB laser. A waveguide structure in the n-doped cladding layer includes a waveguide layer of a first composition compositionally different from the compound semiconductor material having an optical thickness of 0.7 to 1.5 of the guided wavelength. The waveguide structure can further include a hetero-waveguide stack including a plurality of alternating compositional layers beyond the waveguide layer each having a thickness between one quarter and one half the guided wavelength alternating the compound semiconductor material with a second composition defining a composition wavelength.

Abstract: A laser system includes a semiconductor laser having a laser driver coupled thereto. An output of the semiconductor laser is optically coupled to an input of an optical splitter that provides outputs including or coupled to a first branch having a first branch fiber coupled to a feedback reflector which provides a cavity boundary that defines a passive secondary cavity for the semiconductor laser, and a second branch including a back reflection reduction device. The roundtrip attenuation from an output facet of the laser to the feedback reflector is from ?30 dB to ?80 dB. The laser driver provides sufficient drive stability so that a frequency variation of the semiconductor laser is less than one free spectral range (FSR) of the secondary cavity. An output of said system is taken after the back reflection reduction device.

Abstract: A polarization diversity detector includes at least one optical fiber having a first end for receiving a beam of light and a second end for transmitting the beam of light. A collimator receives the beam of the light from the optical fiber and outputs a collimated beam. A polarization diversity element includes a birefringent material which is positioned for receiving the collimated beam and resolving the collimated beam into a first beam having a first polarization and a second beam having a second polarization different from the first polarization. The first beam and second beam are angled relative to one another. At least one photodetector array pair includes a first photodetector array positioned to receive the first beam and a second photodetector array positioned to receive the second beam.

Abstract: A polarization diversity detector includes at least one optical fiber having a first end for receiving a beam of light and a second end for transmitting the beam of light. A collimator receives the beam of the light from the optical fiber and outputs a collimated beam. A polarization diversity element includes a birefringent material which is positioned for receiving the collimated beam and resolving the collimated beam into a first beam having a first polarization and a second beam having a second polarization different from the first polarization. The first beam and second beam are angled relative to one another. At least one photodetector array pair includes a first photodetector array positioned to receive the first beam and a second photodetector array positioned to receive the second beam.