Methods and apparatus for obtaining a vibrational circular dichroism (VCD) image using a discrete frequency infrared (DFIR) microscope are disclosed. The method includes generating a pulsed laser beam comprising a spectral frequency, which may be tunable; modulating the laser beam to generate circularly polarized light; illuminating a sample and collecting, and detecting an optical signal transmitted or transflected from the location of the sample. The detected signal is demodulated at, for example, both the pulse frequency and the sum or difference of the pulse frequency and the modulating frequency to obtain an intensity value that correspond to the absorbance, and a polarization-dependent value that corresponds to the VCD. Other configurations of the apparatus may be employed to measure VCB and VLD.

A photo-thermal speckle spectroscopy device having an infrared laser, a visible laser, a foam, and a camera. The infrared and visible lasers are focused on the foam, which causes the visible laser to scatter. A camera records the speckle pattern, which shifts when the IR laser is turned on. The related method of photo-thermal speckle spectroscopy is also disclosed.

A photo-thermal speckle spectroscopy device having an infrared laser, a visible laser, a foam, and a camera. The infrared and visible lasers are focused on the foam, which causes the visible laser to scatter. A camera records the speckle pattern, which shifts when the IR laser is turned on. The related method of photo-thermal speckle spectroscopy is also disclosed.

A method of spectroscopy, comprises: transmitting output radiation to a sample; collecting from the sample input radiation being indicative of interaction between the output radiation and the sample; modulating at least one of the output radiation and the input radiation, wherein at least one of the output radiation and the modulation is characterized by a scanned parameter; combining the input radiation, following the modulation, with a reference signal to provide a combined signal; processing the combined signal to construct a vector describing a dependence of a radiation property of the input radiation on the parameter; and at least partially identifying the sample or a change in comprises sample based on at least the vector.

A tunable laser source that includes multiple gain elements and uses a spatial light modulator in an external cavity to produce spectrally tunable output is claimed. Several designs of the external cavity are described, targeting different performance characteristics and different manufacturing costs for the device. Compared to existing devices, the tunable laser source produces high output power, wide tuning range, fast tuning rate, and high spectral resolution.

A tunable laser source that includes multiple gain elements and uses a spatial light modulator in an external cavity to produce spectrally tunable output is claimed. Several designs of the external cavity are described, targeting different performance characteristics and different manufacturing costs for the device. Compared to existing devices, the tunable laser source produces high output power, wide tuning range, fast tuning rate, and high spectral resolution.

A method for correcting frequency offset in a dual comb spectroscopy system is provided. The method includes causing a first laser (L1) generator to transmit L1 pulses at a repetition rate of a first frequency and causing a second laser (L2) generator to transmit L2 pulses at a repetition rate of a second frequency. The method also includes interrogating a reference material using a combination of the L1 pulses and the L2 pulses and capturing reference cell pulses. The method further includes interrogating a material of interest using the L1 pulses and capturing material of interest pulses. The method includes determining a frequency jitter based on the captured reference cell pulses and the combination of the captured material of interest pulses and the L2 pulses.

Method and gas analyzer for measuring the concentration of a gas component in a sample gas, wherein to measure the concentration of a gas component in a sample gas, a laser diode is actuated by a current and light generated by the laser diode is guided through the sample gas to a detector, the current is simultaneously varied within periodically successive sampling intervals for the wavelength-dependent sampling of an absorption line of interest of the gas component, and the current can be additionally modulated sinusoidally based on wavelength modulation spectroscopy with a low frequency and small amplitude, such that a measuring signal generated by the detector is evaluated to form a measurement result, where to improve the measuring signal-noise ratio and achieve a much lower detection limit with the same measuring distance, the current is modulated with a high (RF) frequency in the GHz range so that no wavelength modulation occurs, and an RF modulation amplitude is selected at the maximum level using the linear control range of the laser diode where, before evaluation, the measuring signal is demodulated at the radio frequency.

Method and gas analyzer for measuring the concentration of a gas component in a sample gas, wherein to measure the concentration of a gas component in a sample gas, a laser diode is actuated by a current and light generated by the laser diode is guided through the sample gas to a detector, the current is simultaneously varied within periodically successive sampling intervals for the wavelength-dependent sampling of an absorption line of interest of the gas component, and the current can be additionally modulated sinusoidally based on wavelength modulation spectroscopy with a low frequency and small amplitude, such that a measuring signal generated by the detector is evaluated to form a measurement result, where to improve the measuring signal-noise ratio and achieve a much lower detection limit with the same measuring distance, the current is modulated with a high (RF) frequency in the GHz range so that no wavelength modulation occurs, and an RF modulation amplitude is selected at the maximum level using the linear control range of the laser diode where, before evaluation, the measuring signal is demodulated at the radio frequency.

Systems and methods according to exemplary embodiments of the present disclosure can be provided that can efficiently detect the amplitude and phase of a spectral modulation. Such exemplary scheme can be combined with self-interference fluorescence to facilitate a highly sensitive depth localization of self-interfering radiation generated within a sample. The exemplary system and method can facilitate a scan-free depth sensitivity within the focal depth range for microscopy, endoscopy and nanoscopy.