A semiconductor device is provided with at least two photodetectors and an interposed etalon. Signals from the photodetectors may be compared to generate a control signal. The control signal may be used for wavelength control and/or stabilization and for other purposes. According to a preferred embodiment, the etalon is formed of at least two distributed Bragg reflectors. The etalon provides high discrimination power. In addition, the etalon has a periodic discrimination function that may be mat...

Fiber optic grating and etalon based fiber sensor systems are described that include an all solid state demodulation system with no moving parts. This demodulation system is based on using interference patterns generated by reflections from fiber gratings or etalons and measurements using an optical detector array. This demodulation system is applied to dual overlaid fiber optic gratings that have been written onto noncircularly symmetric birefringent optical fibers. These fiber grating based se...

A Saturable Reflector apparatus comprises a substrate having a first and second surfaces, and a reflector having a saturable absorber layer, attached to the first surface. At least one of the first and second surfaces has been modified to enhance an etalon effect of the substrate due to interference of light reflecting from the first and second surfaces. Either or both of the surfaces may be modified, for example, by polishing or coating. The apparatus may also include means for adjusting an opt...

A low-finesse, tri-etalon optical parametric oscillator includes an optical cavity bounded by two coupling mirrors, and a narrow-linewidth pump laser which supplies pump energy to the optical cavity at a pump wavelength. A pair of walk-off compensated, non-linear optical crystals (but not limited to walk-off compensated) is disposed with the cavity and converts energy at the pump wavelength to energy at longer signal and idler wavelengths. The mirrors are configured such that each of the three b...

An optical fiber pressure sensor having a base layer 20 with an optical fiber hole, a fiber stop layer 28 and, optionally, an etch stop layer 24. The fiber stop layer optionally has a fiber stop hole 33 that is smaller than the optical fiber 22. A diaphragm cap layer 32 is bonded to the fiber stop layer 28. The diaphragm cap layer 32 has a diaphragm 34 spaced apart from the optical fiber. The optical fiber and diaphragm form an Etalon that changes cavity length with applied pressure. Optionally,...

An airgap type etalon has a higher degree of design freedom of a wavelength-temperature characteristic so that such a wavelength-temperature characteristic can be freely adjusted. The airgap type etalon includes a fixing block having one flat surface, and a transparent parallel flat plate having parallel flat surfaces formed with an antireflection coating and a reflection augmenting coating thereon, respectively. The flat surface at the antireflection coating side is joined to the flat surface o...

A compact wavelength monitoring and control assembly for a narrow band source is provided comprising a narrow bandpass, wavelength selective transmission filter element, of Fabry-Perot structure, through which two collimated beams from a laser source are directed onto two photodetectors. The differential output of the two photodetectors is used in a feedback loop to stabilize the source to the desired wavelength. Through the dependence of the wavelength transmission of the Fabry-Perot etalon on ...

A compensator for thermal or other uncontrollable effects in a liquid-crystal etalon filter. The narrow pass band of the filter is controlled by adjusting the amplitude of an AC drive signal applied to the electrodes on either side of the liquid crystal in the filter. An optical detector detects the intensity of light from a narrow-bandwidth input beam passed by the detector. Electrical circuitry determines the bipolar amplitude of the component of the light intensity that is at twice the freque...

An optically bistable device comprises a Fabry-Perot etalon containing intracavity liquid crystal material. Etalon mirros of deposited silver are overlaid on indium tin oxide electrodes. The electrodes provide electrical biasing means for the material, which exhibits both optical nonlinearity and electro-optic tunability of refractive index. The etalon has an interference fringe maximum at a wavelength .lambda..sub.m1. the fringe is tunable to .lambda..sub.m2 by applying a bias voltage across th...

The optical path difference between two reflecting surfaces of an etalon 2 is monitored by directing a light beam B onto the etalon, directing the reflected beam Ba from the etalon onto an optical reference wedge 3 and directing the reflected beam Bb from the wedge onto a linear photo-detector array 4. The position along the array 4 of a peak of light intensity represent the location of an interference maximum and corresponds to reflection of light at that position along the length L of the wedg...