A method and apparatus for enhancing the stability of an oscillator circuit by generating a comb of frequencies in a non-linear resonator member in response to a drive frequency, the oscillator circuit including a voltage controlled oscillator which is locked to a particular tooth of the comb of frequencies produced by the non-linear resonator member at a drive frequency for which the absolute value of the first derivative of the drive frequency versus said comb frequency is greater than 1, and wherein the second voltage controlled oscillator is coupled with a phase locked loop circuit which controls the locking of the second voltage controlled oscillator to said particular tooth of the comb of frequencies.

Techniques for generating an arbitrary target electromagnetic signal with a nonlinear material, include determining a time varying target amplitude and target phase and an order n of a nonlinear material. For each time, a first set of nth roots of the target amplitude and a second set of nth roots of the target phase are determined. An input amplitude based on one value from the first set and an input phase based on one value from the second set is determined at each time. A difference between temporally successive values of phase is minimized. An electromagnetic signal is modulated to impose the input amplitude and phase to produce a modulated electromagnetic input signal that is introduced into the nonlinear material to produce a target electromagnetic signal.

A laser device for optical communication comprises a first laser unit connected to a first optical fiber for supplying a transmission laser beam thereto. wherein the laser device is configured for providing a reference laser beam in addition to the transmission laser beam. For providing the reference laser beam the laser device further includes a second laser unit connected to a second optical fiber for supplying the reference laser beam to the second optical fiber. The first laser unit is configured for providing the transmission laser beam as a linear polarized beam that is polarized in a first polarization direction, and the second laser unit is configured for providing the reference laser beam as a linear polarized beam that is polarized in a second polarization direction. The first optical fiber and the second optical fiber are formed of polarization maintaining optical fibers, and the laser device further includes a polarization combiner connected to a third polarization maintaining optical fiber for conveying the transmission laser beam and the reference laser beam to an optical output of the laser device.

A laser driving device and a method for enabling a uniform light field, wherein the laser driving device is a high-power laser driving device that enables a uniform light field on the basis of a narrow-band low-spatial-coherence light and is provided for laser fusion. The narrow-band low-spatial-coherence light is configured as a seed of the laser driving device, an amplification and transmission unit amplifies the seed, a frequency conversion unit converts a frequency of the laser, and a focusing component is configured for laser focusing and uniform illumination.

The invention relates to a device and corresponding method for raster-scan optoacoustic imaging, the device comprising: a radiation source comprising at least one Raman laser source, the radiation source being configured to generate a plurality of pulses of electromagnetic radiation, each of the pulses comprising portions of electromagnetic radiation at two or more distinct wavelengths, and at least one acousto-optic tunable filter configured to select, from at least one of the pulses, one of the portions of electromagnetic radiation at one of the wavelengths; an irradiation unit configured to irradiate a region of interest of an object, in particular a biological tissue, with the selected portion of electromagnetic radiation of the at least one pulse; a detection unit configured to detect acoustic waves emitted from the region of interest in response to irradiating the region of interest with the selected portion of electromagnetic radiation of the at least one pulse; and a scanning unit configured to move the irradiation unit and detection unit, on the one hand, and/or the region of interest, on the other hand, along at least one dimension relative to each other so as to position the irradiation unit and detection unit at a plurality of different locations along the at least one dimension relative to the region of interest, and to control the detection unit to detect the acoustic waves at the plurality of locations.

The present disclosure provides for materials (e.g., films, mixtures, and colloidally suspended in solution) including two types of particles (e.g., nanoparticles) that exhibit harmonic surface plasmon resonances (SPR), where these are referred to as harmonically paired set of particles. The present disclosure provides for harmonically paired set of particles, where the particles are separated by a dielectric layer. The dielectric layer has a thickness such that direct electron transfer does not occur between the harmonically paired set of particles. The harmonically paired set of particles can be included in harmonically paired set of particle system or devices which can be a component in measurement systems or devices.

A frequency conversion device, including a source of a pump beam of electromagnetic radiation of a first wavelength, and an array of mutually spaced semiconductor islands including at least one III-V semiconductor compound and configured so that the pump beam of electromagnetic radiation of the first wavelength incident upon the semiconductor islands and electromagnetic radiation of a second wavelength incident upon the semiconductor islands cause the semiconductor islands to emit electromagnetic radiation of a third wavelength different to the first and second wavelengths by at least one of a sum frequency generation process and a difference frequency generation process, wherein the semiconductor islands are supported by a transparent support such that the support is substantially transparent to radiation of the third wavelength, wherein at least the radiation of the third wavelength passes through the transparent support.

A nonlinear crystal comprising a first end face and an opposing second end face is described. The first and second end faces are separated along an optical axis of the nonlinear crystal by a length in the range of 0.25 mm and 2 mm. Although the length of the nonlinear crystal results in a reduction in the nonlinear effects induced on an optical field propagating through the crystal it also provides for reduced deviation experienced by the generated optical field when the nonlinear crystal is rotated. Therefore, when the nonlinear crystals are incorporated within an enhancement cavity their reduced length allows for the deviation of the output field to be minimised by servo control electronics arranged to adjust a single cavity mirror. This significantly reduces the complexity, and thus expensive of the servo control electronics when compared to those employed with the prior art enhancement cavities.

Systems and methods for precision control of microresonator (MR) based frequency combs can implement optimized MR actuators or MR modulators to control long-term locking of carrier envelope offset frequency, repetition rate, or resonance offset frequency of the MR. MR modulators can also be used for amplitude noise control. MR parameters can be locked to external reference frequencies such as a continuous wave laser or a microwave reference. MR parameters can be selected to reduce cross talk between the MR parameters, facilitating long-term locking. The MR can be locked to an external two wavelength delayed self-heterodyne interferometer for low noise microwave generation. An MR-based frequency comb can be tuned by a substantial fraction or more of the free spectral range (FSR) via a feedback control system. Scanning MR frequency combs can be applied to dead-zone free spectroscopy, multi-wavelength LIDAR, high precision optical clocks, or low phase noise microwave sources.

Based on graphene heterostructure in chip-scale silicon nitride microresonators, optoelectronic control and modulation in frequency combs via group velocity dispersion modulation can be demonstrated. By tuning graphene Fermi level from 0.50 eV to 0.65 eV via electric-field gating, deterministic in-cavity group velocity dispersion control from anomalous (−62 fs.sup.2/mm) to normal (+9 fs.sup.2/mm) can be achieved with Q factor remaining high at 10.sup.6. Consequently, both the primary comb lines and the full comb spectra can be controllable dynamically with the on/off switching of the Cherenkov radiation, the tuning of the primary comb lines from 2.3 THz to 7.2 THz, and the comb span control from zero comb lines to ˜781 phase-locked comb lines, directly via the DC voltage.