An optical system uses a sample medium disposed within an optical cavity, receives an input beam that may be non-coherent or coherent, and produces an optical energy from the input beam, by creating birefringent-induced beam components each cavity traversal, forming a mixed quantum state beam for the input beam. The mixed quantum state beam exits the cavity, and the energy distribution of the exiting beam is analyzed over a range of tuned input beam frequencies to uniquely identify circularly birefringent the materials within the sample medium, e.g., amino acids, proteins, or other circular birefringent molecules, biological or otherwise.

According to a method for cavity enhanced microscopy, a sample is arranged on a sample carrier of an optical cavity, which is formed by a pair of opposing mirrors. A description defining a lateral motion of the sample during a predefined time interval and a variation of the cavity length during the time interval in a temporally synchronized manner is stored and an actuator system is triggered to move the sample carrier and/or at least one mirror of the pair of mirrors to effect the lateral motion of the sample with respect to the cavity and the variation of the cavity length according to the description. Light is introduced into the cavity and transmitted portions and/or reflected portions and/or scattered portions and/or emitted portions are detected to generate a sensor dataset.

The present disclosure provides an apparatus and a method for measuring a concentration of pollutants in water. A passive Q-switched fiber laser outputs an evanescent wave to a to-be-tested water sample after emitting a Q-switched pulse laser signal and transmitting it via an evanescent field fiber, and based on an evanescent wave change caused by an absorption effect of the pollutants in the to-be-tested water sample to the evanescent wave and an output repetition frequency change of the passive Q-switched fiber laser due to the evanescent wave change, outputs an output repetition frequency result of the passive Q-switched fiber laser. The method is simple; and the apparatus based on the method is simple in structure and low in cost.

The optical cell of an elongated shape has an inner space into which gas is introduced and includes: a cell main body forming the inner space; a manifold member being separably connected to an outer surface of the cell main body extending in a longitudinal direction; and a heating mechanism heating the manifold member, in which the cell main body has a through hole penetrating from the outer surface into the inner space, and the manifold member has a gas introduction path extending along the longitudinal direction and guiding the gas, which has been taken in from the outside, from one side to another side in the longitudinal direction and then guiding the gas to the inner space through the through hole.

A laser system with optical feedback, includes an optical-feedback-sensitive laser which emits, via an output optical fibre, a continuous, frequency-adjustable, propagating, source optical wave, known as the source wave; a resonant optical cavity coupled by means of optical feedback to the laser and configured to generate an intra-cavity wave, one fraction of which returns to the laser in the form of a counter-propagating optical wave; an electro-optic fibre modulator placed on the optical path between the laser and the resonant optical cavity, the electro-optic modulator being configured to generate a phase-shifted source wave by phase-shifting the source wave and, by phase-shifting the counter-propagating optical wave, to generate a phase-shifted counter-propagating wave, known as the feedback wave, which reaches the laser; a phase-control device for generating a control signal for the electro-optic modulator from an error signal representative of the relative phase between the source wave and the feedback wave, such as to cancel the relative phase between the source wave and the feedback wave.

An apparatus for quantitatively detecting isotopologue of carbon dioxide using dual-photon absorption, comprising a laser source, a laser frequency stabilizer, a sample chamber, a signal detector, and a signal analyzer. The sample chamber comprises an optical resonator and a piezoelectric ceramic. The laser source is configured to output a laser beam. The laser frequency stabilizer is configured to lock the laser beam to a mode frequency of the optical resonator. The piezoelectric ceramic is configured to adjust a length of the optical resonator to alter the mode frequency of the optical resonator to match energy levels of a target molecular isotopologue. The signal detector is configured to detect a transmission intensity of the light beam passing the optical resonator to obtain a dual-photon absorption signal. The signal analyzer is configured to analyze and process the dual-photon absorption signal to obtain a concentration of the target molecular isotopologue.

The present disclosure provides an apparatus and a method for measuring a concentration of pollutants in water. A passive Q-switched fiber laser outputs an evanescent wave to a to-be-tested water sample after emitting a Q-switched pulse laser signal and transmitting it via an evanescent field fiber, and based on an evanescent wave change caused by an absorption effect of the pollutants in the to-be-tested water sample to the evanescent wave and an output repetition frequency change of the passive Q-switched fiber laser due to the evanescent wave change, outputs an output repetition frequency result of the passive Q-switched fiber laser. The method is simple; and the apparatus based on the method is simple in structure and low in cost.

An interferometric fluid sensing system includes: a laser; a plurality of first fibre portions arranged to receive laser light from the laser; a second fibre portion configured to provide a reference arm for the interferometric fluid sensing system; and a detector arranged to receive light from the first and second fibre portions, wherein the laser light that passes through a void of each first fibre portion is caused to interfere with light passing through the second fibre portion at or before reaching the detector, wherein each of the first fibre portions is arranged such that that light passing through the void of each first fibre portion travels from the laser to the detector over a different path length from the light passing through the voids of the other first fibre portions.

A method for determining a sulfur trioxide content in a gas. A sample of the gas is taken, and a gas pressure of the sample is reduced. A wave number-resolved transmission measurement is carried out on the sample using a wave number-tunable monochrome light source, and a sulfur trioxide content is derived from the measurement. The measurement is carried out in the sulfur trioxide absorption band between 1360 and 1410 cm.sup.1, in particular in a window around the sulfur trioxide absorption at 1365.49 cm.sup.1. A method for operating a power plant, a measuring system for determining a sulfur trioxide content in a gas, and a power plant are adapted to determine a sulfur trioxide content in a gas.

A method of generating laser pulses (1) includes: creating a circulating light field in resonator device (11) having resonator length L and an intra-cavity dispersion and configured for supporting light field resonator modes, and generating a pulse train of laser pulses (1) by a mode-locking mechanism. Laser pulses (1) are generated with a repetition frequency and provide a frequency comb with carrier frequency .sub.o and comb modes in frequency space. The intra-cavity dispersion is selected such that round trip phases have a dependency on frequency according to $\left(\right)=m\left(\sqrt{1+4\frac{-{}_0}{m{}_r}}-1\right)+\frac{L}{c}{}_0$
wherein m is an integer providing effective repetition rate (m.sub.r) in combination with mode spacing .sub.r at optical carrier frequency (.sub.o), and the mode-locking mechanism provides a coupling of the resonator modes whereby frequency difference (n=.sub.n+1.sub.n) between neighboring mode frequencie