Method and apparatus for determining the wavelength of a light beam are provided. An input light beam is received, and light from the input light beam is distributed to multiple channels. At a first pair of interferometer cavities that has a first free spectral range, two of the multiple channels of light are received. The intensity of light reflected from the first pair of cavities is measured, and a first estimate of the wavelength or optical frequency of the input light beam is determined based on measurements of interference signals from the first pair of cavities and an initial estimate of the wavelength or optical frequency. At a second pair of cavities that has a second free spectral range smaller than the first free spectral range, another two of the multiple channels of light are received. The intensity of light from the second pair of cavities is measured, and a second estimate of the wavelength or optical frequency of the input light beam is determined based on the first estimate and measurements of interference signals from the second pair of cavities, in which the second estimate is more accurate than the first estimate.

A system comprises an electromagnetic radiation source, a polarizing element, a mode converter, an optical fiber, and a measurement device. The polarizing element receives electromagnetic radiation produced by the electromagnetic radiation source and outputs linearly-polarized electromagnetic radiation having a linear polarization angle .sub.1. The mode converter converts the linearly-polarized electromagnetic radiation to an orbital angular momentum (OAM) mode of linearly-polarized electromagnetic radiation with topological charge L.sub.i. The OAM mode of linearly-polarized electromagnetic radiation is a superposition of first and second OAM modes with topological charges L.sub.i and opposite circular polarizations. The optical fiber supports propagation of the first and second OAM modes with an absolute effective index difference n.sub.eff greater than or equal to 510.sup.3, such that linearly-polarized electromagnetic radiation with linear polarization angle .sub.2 is emitted by the optical fiber. The measurement device is configured to determine a property of the electromagnetic radiation based on the polarization angle .sub.2.

A system comprises an electromagnetic radiation source, a polarizing element, a mode converter, an optical fiber, and a measurement device. The polarizing element receives electromagnetic radiation produced by the electromagnetic radiation source and outputs linearly-polarized electromagnetic radiation having a linear polarization angle .sub.1. The mode converter converts the linearly-polarized electromagnetic radiation to an orbital angular momentum (OAM) mode of linearly-polarized electromagnetic radiation with topological charge L.sub.i. The OAM mode of linearly-polarized electromagnetic radiation is a superposition of first and second OAM modes with topological charges L.sub.i and opposite circular polarizations. The optical fiber supports propagation of the first and second OAM modes with an absolute effective index difference n.sub.eff greater than or equal to 510.sup.5, such that linearly-polarized electromagnetic radiation with linear polarization angle .sub.2 is emitted by the optical fiber. The measurement device is configured to determine a property of the electromagnetic radiation based on the polarization angle .sub.2.

A spectroscope for measuring a spectrum of input light includes a fringe former that forms first fringes having a first pitch by splitting the input light, a diffraction grating that disperses each of the first fringes, a moire pattern former that forms a moire pattern by overlaying the first fringes that have been dispersed, on second fringes having a second pitch different from the first pitch, and an image pickup device that measures the spectrum of the input light by detecting the moire pattern. At least one of the fringe former and the moire pattern former includes a cylindrical lens array.

The invention relates to an optoelectronic chip comprising the following elements: a light inlet; a wavelength-sensitive optical filter; a first photoelectric element for measuring a first light intensity, particularly a first photodiode, the first photoelectric element being arranged such that light penetrating the optoelectronic chip via the light inlet, transmitted by the filter, hits the first photoelectric element; and a second photoelectric element for measuring a second light intensity, particularly a second photodiode, the second photoelectric element being arranged such that the light penetrating the optoelectronic chip via the light inlet, which is reflected by the filter, hits the second photoelectric element.

A laser system comprising two phase-locked solid-state laser sources is described. The laser system can be phase-locked at a predetermined offset between the operating frequencies of the lasers. This is achieved with high precision while exhibiting both low noise and high agility around the predetermined offset frequency. A pulse generator can be employed to generate a series of optical pulses from the laser system, the number, duration and shape of which can all be selected by a user. A phase-lock feedback loop provides a means for predetermined frequency chirps and phase shifts to be introduced throughout a sequence of generated pulses. The laser system can be made highly automated. The above features render the laser system ideally suited for use within coherent control two-state quantum systems, for example atomic interferometry, gyroscopes, precision gravimeters gravity gradiometers and quantum information processing and in particular the generation and control of quantum bits.

A process for characterizing an optical source including a fixed cavity having a free spectral range, the process including: generating a first radiation; receiving at least a portion of this first radiation by at least one sensor; measuring a signal by each sensor and for each scanned state of the source; on the basis of the signals measured, and for each scanned state of the source, calculating a first data item which represents the wavelength of the first radiation, the calculation including, for each scanned state of the source, a selection of a selected value of the first data item from a plurality of possible values, the selection including the elimination of the values of the first data item which do not correspond to a modulo constant of the free spectral range of the fixed cavity expressed according to the units of the first data item.

A laser detection system and method of two way communication comprising: a Mach Zehnder interferometer, the Mach Zehnder interferometer comprising: an entry beam splitter for splitting incident light into a first arm, having an arm length L1 and a second arm having an arm length L2; a modulation stage for receiving a modulation signal and applying a phase difference to the second arm, the magnitude of the phase difference depending upon the magnitude of the modulation signal; an exit beam splitter for recombining light from the first arm with light from the second arm to create a first output and a second output; a detection stage comprising a first detector at the first output for detecting intensity modulation caused by interference of the recombined light; and a signal processor communicably connected to both the modulation stage and the detection stage.

Conventionally, wavelength locking and monitoring has been achieved used various components, including calibrated etalon filters, gratings, and arrays of color filters, which offer fairly bulky solutions that require complicated controls. An improved on-chip wavelength monitor comprises: a combination comb filter comprising a plurality of comb filters, each for receiving a test beams, and each comb filter including a substantially different FSR, e.g. 10 to 20 the next closest FSR. A controller dithers a phase tuning section of each comb filter to generate a maximum or minimum output in a corresponding photodetector indicative of the wavelength of the test signal.

A quantitative phase image generating method for a microscope, includes: irradiating an object with illumination light; disposing a focal point of an objective lens at each of a plurality of positions that are mutually separated by gaps z along an optical axis of the objective lens, and detecting light from the object; generating sets of light intensity distribution data corresponding to each of the plurality of positions based upon the detected light; and generating a quantitative phase image based upon the light intensity distribution data; wherein the gap z is set based upon setting information of the microscope.