366 results about "Optical frequencies" patented technology

Apparatus, method, logic arrangement and storage medium are provided for increasing the sensitivity in the detection of optical coherence tomography and low coherence interferometry (“LCI”) signals by detecting a parallel set of spectral bands, each band being a unique combination of optical frequencies. The LCI broad bandwidth source can be split into N spectral bands. The N spectral bands can be individually detected and processed to provide an increase in the signal-to-noise ratio by a factor of N. Each spectral band may be detected by a separate photo detector and amplified. For each spectral band, the signal can be band p3 filtered around the signal band by analog electronics and digitized, or, alternatively, the signal may be digitized and band pass filtered in software. As a consequence, the shot noise contribution to the signal is likely reduced by a factor equal to the number of spectral bands, while the signal amplitude can remain the same. The reduction of the shot noise increases the dynamic range and sensitivity of the system.

A process for operation of a laser device (1) is described, whereby circulating light pulses each comprising spectral components according to a plurality of longitudinal modes of a resonator configuration (3) are generated in the resonator configuration (3) and subjected to a compensation of group velocity dispersion, and a predetermined linear dispersion is introduced into the light path of the resonator configuration (3), so that at least one mode has a predetermined frequency and/or the mode distance between the modes has a predetermined value. Furthermore, regulations for stabilizing the laser device on the basis of this process and applications of the regulations for the generation for stabilized, ultra-short light pulses, generation of optical frequencies and in the frequency and/or time measuring technique as well as in the spectroscopy are described.

In order to characterize the optical characteristics of a device, a source of light having a variable frequency with a polarization state which varies linearly with frequency is provided as an input to the device under test. The input light is also passed through a known reference path and is added to the light output from the device under test in a beam combiner. The combined light for the frequencies of interest is split into two orthogonal polarizations which are then detected in a spectral acquisition apparatus and supplied to a microprocessor. The spectral measurements are digitized and curve-fitted to provide optical power versus optical frequency curves. Fourier transforms of each of the curves are calculated by the microprocessor. From the Fourier transforms, the four arrays of constants are calculated for the Jones matrix characterizing the device under test.

Apparatus and method for increasing the sensitivity in the detection of optical coherence tomography and low coherence interferometry (“LCI”) signals by detecting a parallel set of spectral bands, each band being a unique combination of optical frequencies. The LCI broad bandwidth source is split into N spectral bands. The N spectral bands are individually detected and processed to provide an increase in the signal-to-noise ratio by a factor of N. Each spectral band is detected by a separate photo detector and amplified. For each spectral band the signal is band pass filtered around the signal band by analog electronics and digitized, or, alternatively, the signal may be digitized and band pass filtered in software. As a consequence, the shot noise contribution to the signal is reduced by a factor equal to the number of spectral bands. The signal remains the same. The reduction of the shot noise increases the dynamic range and sensitivity of the system.

An apparatus, system, computer program, and method for providing a Multimedia over Coax Alliance (MoCA) (or other multimedia-over-coaxial cable technology) network in conjunction with an optical network. In example embodiments, MoCA data is communicated between network nodes in an optical signal. In other example embodiments, MoCA data, or other data, is transmitted in optical frequencies above 860 MHz.

The invention allows for the accurate, real-time readout of the optical frequency of a swept-wavelength laser device by counting the number of fringes of a calibrated etalon that occur as the laser is swept. The distinguishing feature of the present invention is that the etalon fringe signal is phase-locked to a slave signal of a higher multiple frequency. The higher frequency of the slave signal divides the frequency interval of the etalon fringe spacing by the additional frequency multiple. The slave signal therefore generates a scale for optical frequency that is of higher resolution than possible with the etalon alone. The phase-lock also insures that the slave signal tracks monotonic scans of the optical frequency regardless of scan profile.

The invention also allows for the precise, real-time control of the optical frequency of a laser during the sweep of the laser. By comparing a signal proportional to the transmission of light through a calibrated Fabry-Perot etalon to a reference control signal, the phase difference between etalon transmission signal and the reference signal may be fed back to the laser to drive the phase difference to zero (phase-lock). The phase-lock ensures that the optical frequency profile of the sweep follows exactly the frequency profile of the reference signal. Tailoring the input reference signal controls the velocity of the optical-frequency sweep.

A method of selecting components for a multivariate optical computing and analysis system to isolate a spectral region includes selecting a spectral region of interest; selecting a spectral element with a predetermined transmission characteristic to control a spectral range of an illumination source; illuminating a sample with the illumination source; and analyzing an optical frequency returned by the sample relative to the spectral region of interest.

A two-optical signal generator is provided for generating two optical signals, where a difference between optical frequencies or optical wavelength of the two optical signals can be adjusted. A first optical modulator modulates a single-mode optical signal generated by a first light source according to an inputted signal, and outputs a modulated optical signal including predetermined specific two optical signals having a predetermined optical frequency difference, while a second light source generates a multi-mode optical signal including predetermined two further optical signals having substantially the same wavelengths as those of the predetermined specific two optical signals of the modulated optical signal, respectively. Then an optical injection device optically injects the modulated optical signal into the second light source, and the predetermined specific two optical signals of the modulated optical signal are injection-locked into the predetermined two further optical signals of the multi-mode optical signal, so that the second light source generates an injection-locked predetermined specific two optical signals.

The present invention is directed to a heterodyne reflectometer system and method for obtaining highly accurate phase shift information from heterodyned optical signals, from which extremely accurate film depths can be calculated. A linearly polarized light comprised of two linearly polarized components that are orthogonal to each other, with split optical frequencies, is directed toward a film causing one of the optical polarization components to lag behind the other due to an increase in the optical path in the film for that component. A pair of detectors receives the beam reflected from the film layer and produces a measurement signal, and the beam prior to incidence on the film layer and generates a reference signal, respectively. The measurement signal and reference signal are analyzed by a phase detector for phase shift. The detected phase shift is then fed into a thickness calculator for film thickness results. A grating interferometer may be included with the heterodyne reflectometer system with a grating, which diffracts the reflected beam into zeroth- and first-order bands, which are then detected by separate detectors. A detector receives the zeroth-order beam and generates another measurement signal. Another detector receives the first-order beam and generates a grating signal. The measurement signal from the grating and reference signal may be analyzed by a phase detector for phase shift, which is related to the thickness of the film. Conversely, either measurement signal may be analyzed with the grating signal by a phase detector for detecting a grating phase shift. The refractive index for the film may be calculated from grating phase shift and the heterodyne phase shift. The updated refractive index is then used for calculating thickness.

The present invention provides a Raman amplifier and the like comprising a structure for keeping the flatness of power spectrum of Raman-amplified signal light. The Raman amplifier comprises an optical fiber for Raman-amplifying a plurality of signal channels of signal light having respective center optical frequencies different from each other; a pumping light supply section for supplying N (N being an integer of 2 or more) pumping channels of pumping light having respective center optical frequencies different from each other to the optical fiber; and a feedback section for detecting a part of the signal light Raman-amplified within the optical fiber when the pumping light is supplied thereto, and controlling the pumping light supply section such that the Raman-amplified signal light has a substantially flat power spectrum with respect to an optical frequency direction according to the result of detection. In particular, the feedback section divides the detected Raman-amplified signal light into N optical frequency ranges defined so as to include respective Raman amplification peaks as optical frequencies lower than respective center optical frequencies of the pumping channels of pumping light by an optical frequency shift of about 15 THz, and controls the pumping light supply section such that the Raman-amplified signal light has a power fluctuation of 2 dB or less in each of thus divided N optical frequency ranges.

An array of antenna elements (20) can be used to detect subwavelength sized anomalies on a surface below the array. An array (20) is illuminated at optical frequencies by a coherent optical energy source (26). The change in reactance and radiated power of the antenna elements that results from the proximity of the anomaly to the near field of the antenna element's open-circuited is detected and holographically filtered to eliminate the radiation caused by the antenna array itself. Image processing is performed on the detected scattered radiation (100) to determine whether an anomaly is present and to locate the anomaly and its characteristics.

A polarization-related characteristic of an optical path is determined from a predetermined function of the mean-square of a plurality of differences between polarization-analyzed optical power parameters corresponding to pairs of wavelengths mutually spaced about a midpoint wavelength by a small optical frequency difference. At least some of the said differences correspond to wavelength pairs measured under conditions where at least one of midpoint wavelength, input state of polarization (I-SOP) or analyzed state of polarization (A-SOP) of a pair is different.

The invention concerns a laser system with a frequency comb generator for generating a comb of optical frequencies having an offset frequency and a plurality of equidistant modes, wherein the laser system further preferably comprises at least one stabilizer for stabilizing the frequency comb onto a certain offset frequency and/or onto a certain mode spacing. The laser system further comprises an optical amplifier for amplifying the frequency comb coupled out of the frequency comb generator, the amplification factor of this amplifier being variable; and the amplifier is followed by a Raman medium for generating a Raman shift of the frequency comb.

There are provided a method and a system for characterizing the CMRR of an ICR under test, which employ highly coherent light from two continuous-wave (CW) single-frequency lasers whose respective optical frequencies mutually differ by an offset defining an “Intermediate Frequency” (f_IF) in the rf electrical baseband. The method involves the coherent mixing of light from these two lasers in the ICR under test. A “tone” in the rf electrical baseband at frequency f_IF is generated by the beating of light from the two single-frequency lasers as they interfere on the photodetectors of the ICR. The resulting tone at frequency f_IF in the output electrical signals of the ICR is then detected and analyzed to characterize the CMRR of the ICR.

There is provided a narrow linewidth semiconductor laser device comprising a semiconductor laser and a low noise current source operatively connected to the laser for supplying current thereto, the current source being particularly adapted to prevent a significant degradation of the frequency noise spectrum of the laser. The laser device also has an optical frequency discriminator providing an error signal representative of the optical frequency of the laser. The laser device also has control means having a feedback network for providing a frequency feedback signal. The feedback network is particularly adapted to the frequency noise spectrum of the frequency discriminator, the frequency noise spectrum of the laser and the tuning response of the laser. The control means is also provided with sequencing means for allowing to automatically enable frequency locking of the laser on the frequency reference of the optical frequency discriminator. The laser device is provided with an enclosure for enclosing the frequency discriminator to isolate the frequency discriminator from external perturbations. Such an arrangement is particularly advantageous since it allows to provide an improved sub-kHz linewidth and a high coherence while being compact, lightweight and highly reliable. Moreover, the narrow linewidth semiconductor laser device of the present invention can advantageously be automatically operated.

The invention relates to the non linear optical frequency conversion. To realize output of high power THz wave which can be continuously tuned, and stable running at room temperature, the technical scheme used by the invention is that: a tunable terahertz radiation source based on difference frequency cherenkov effect is composed of a laser device, a frequency doubling crystal, a double wavelength parametric oscillator, a harmonic mirror, a polarization filter, a combined beam mirror, a column lens and a difference frequency crystal; the harmonic mirror is placed between the frequency doubling crystal and the double wavelength parametric oscillator; the double wavelength parametric oscillator is II type phase matching KTP (Potassium Titanyl Phosphate) crystal OPO (Optical Parametric Oscillator); the polarization filter, the combined beam mirror and the column lens are arranged between the parametric oscillator and the difference frequency crystal; the difference frequency crystal is amagnesium oxide doped lithium niobate crystal with molecular formula of MgO:LiNbO3 or MgO:LN, and the generated THz wave is coupled and output by an Si prism on the side surface of the difference frequency crystal. The tunable terahertz radiation source based on difference frequency cherenkov effect is mainly applied to the optical frequency conversion.