Abstract: A method for operating a data processing system to simulate a physical system is disclosed. The physical system receives a time-varying input and generates a time-varying output. A model of the physical system is provided. The model depends on values of the time-varying input and an internal state in the physical system, the internal state is not directly measurable. The model includes a bi-quad component that models a resonance or anti-resonance of the physical system. For each of a plurality of time points, a current input value for the time-varying input is received. An internal state vector having a value of the internal state at a current time point as one component thereof is computed and computing an estimate of a system output at that time point, the system output being directly measurable. In one aspect of the invention, the internal state vector depends on a previous value of the internal state vector and the current input value.

Abstract: A polarization control system includes a light source that generates two light beams with different polarization states and optical frequencies. A polarization state modulator changes the polarization states of the two light beams. A first detector path generates a first beat signal from the two light beams passing through a first polarizer. A second detector path generates a second beat signal from the two light beams passing through a second polarizer that is oriented substantially orthogonal to the first polarizer. An amplitude detector generates an amplitude beat signal from the first and the second beat signals. The system then uses the amplitude beat signal to determine how to adjust the polarization state modulator in order to generate the first and the second light beams with the desired polarization states.

Abstract: Directing an input light beam into a laser diode operated at a power below that required for lasing stimulates emissions, resulting in an amplified output beam. A dynamic steering system can focus the input beam onto front face of the laser diode. The steering system optionally includes an optical element mounted solely on piezoelectric actuators. Control signals for the actuators in the steering system control a base position and cause alternating movements of the optical element. A detector measuring optical power leaking from a back face of the laser diode can determine the power of the amplified beam that exits from the front face, and derivatives of the measured power with respect to the alternating movements indicate required adjustments of the base position. A polarizing beam splitter and quarter-wave plate in the path of beams can separate the input and amplified beams.

Abstract: A method for improving polarization extinction ratio includes changing a polarization state of a light beam, wherein the light beam thereafter includes spatially non-uniform polarization states, and spatially filtering the light beam to filter out the spatially non-uniform polarization states. Spatial filtering involves filtering a wavefront of the light beam by passing the light beam through a polarization-maintaining single-mode fiber, or filtering an amplitude of the light beam by passing the light beam through an aperture.

Abstract: A polarization control system includes a beam source that generates a first beam component containing light with a first polarization and a first frequency and a second beam component containing light with a second polarization and a second frequency. A polarization state modulator adjusts the polarizations of the components for transmission on a single optical fiber. A detector system measures polarizations of the components when output from the optical fiber and determines how to adjust the polarization state modulator in order to give the first and the second components the desired output polarization states. The beam source can be implemented using a Zeeman-split laser, a laser containing a birefringent element, a pair of phase-locked lasers, and/or a variety of configurations of electro-optic or acousto-optic crystals operated to create or enhance the frequency difference between the beam components.

Abstract: A polarization control system includes a light source that generates two light beams with different polarization states and optical frequencies. A polarization state modulator changes the polarization states of the two light beams. Three detector paths generate a first beat signal, a second beat signal, and a third beat signal from the two light beams. An amplitude detector determines the amplitude of the first beat signal at a beat frequency. A phase comparator determines the phase difference between the second and the third beat signals. The system then uses the amplitude and the phase difference to determine how to adjust the polarization state modulator in order to generate the first and the second light beams with the desired polarization states.

Abstract: A polarization control system includes a beam source that generates a first beam component containing light with a first polarization and a first frequency and a second beam component containing light with a second polarization and a second frequency. A polarization state modulator adjusts the polarizations of the components for transmission on a single optical fiber. A detector system measures polarizations of the components when output from the optical fiber and determines how to adjust the polarization state modulator in order to give the first and the second components the desired output polarization states. The beam source can be implemented using a Zeeman-split laser, a laser containing a birefringent element, a pair of phase-locked lasers, and/or a variety of configurations of electro-optic or acousto-optic crystals operated to create or enhance the frequency difference between the beam components.

Abstract: An interferometer returns parallel beams that are subject to walk-off caused by reflector misalignment for an additional pass through the interferometer optics and thereby eliminates beam walk-off. A return reflector can be a plane mirror that directs returning beams to retrace paths through the interferometer optics to combine and exit along the axis of the input beam. Separation optics can separate the combined beam from the input beam. Alternatively, a return reflector such as an isosceles prism or a trapezoidal prism reflects and offsets returning beams so that the combined beam is offset from the input beam. The return reflector more generally responds to a shift in incident beam position with a matching shift of the reflected beam in contrast to a retroreflector, which shifts a reflected beam in a direction opposite to the shift in the incident beam.

Abstract: A polarization control system includes a beam source that generates a first beam component containing light with a first polarization and a first frequency and a second beam component containing light with a second polarization and a second frequency. A polarization state modulator adjusts the polarizations of the components for transmission on a single optical fiber. A detector system measures polarizations of the components when output from the optical fiber and determines how to adjust the polarization state modulator in order to give the first and the second components the desired output polarization states. The beam source can be implemented using a Zeeman-split laser, a laser containing a birefringent element, a pair of phase-locked lasers, and/or a variety of configurations of electro-optic or acousto-optic crystals operated to create or enhance the frequency difference between the beam components.

Abstract: A polarization control system includes a light source that generates two light beams with different polarization states and optical frequencies. A polarization state modulator changes the polarization states of the two light beams. Three detector paths generate a first beat signal, a second beat signal, and a third beat signal from the two light beams. An amplitude detector determines the amplitude of the first beat signal at a beat frequency. A phase comparator determines the phase difference between the second and the third beat signals. The system then uses the amplitude and the phase difference to determine how to adjust the polarization state modulator in order to generate the first and the second light beams with the desired polarization states.

Abstract: An interferometer returns parallel beams that are subject to walk-off caused by reflector misalignment for an additional pass through the interferometer optics and thereby eliminates beam walk-off. A return reflector can be a plane mirror that directs returning beams to retrace paths through the interferometer optics to combine and exit along the axis of the input beam. Separation optics can separate the combined beam from the input beam. Alternatively, a return reflector such as an isosceles prism or a trapezoidal prism reflects and offsets returning beams so that the combined beam is offset from the input beam. The return reflector more generally responds to a shift in incident beam position with a matching shift of the reflected beam in contrast to a retroreflector, which shifts a reflected beam in a direction opposite to the shift in the incident beam.