Mid-infrared photothermal heterodyne imaging (MIR-PHI) techniques described herein overcome the diffraction limit of traditional MIR imaging and uses visible photodiodes as detectors. MIR-PHI experiments are shown that achieve high sensitivity, sub-diffraction limit spatial resolution, and high acquisition speed. Sensitive, affordable, and widely applicable, photothermal imaging techniques described herein can serve as a useful imaging tool for biological systems and other submicron-scale applications.

System for performing chemical spectroscopy on samples from the scale of nanometers to millimeters or more with a multifunctional platform combining analytical and imaging techniques including dual beam photo-thermal spectroscopy with confocal microscopy, Raman spectroscopy, fluorescence detection, various vacuum analytical techniques and/or mass spectrometry. In embodiments described herein, the light beams of a dual-beam system are used for heating and sensing.

A passive-phase-detection photothermal spectroscopy (PTS) system and methods are provided for gas measurements. The PTS system includes a pump laser source, a probe laser source, the pump and probe laser beams simultaneously propagating through an optical waveguide having a target gas specimen. Moreover, the PTS system can be based on a heterodyne detection scheme and includes a combiner configured to align light input from a local oscillator with the probe laser beam output from the optical waveguide to output to a photodetector that is configured to generate beat notes. A demodulation module is configured to detect and measure a photothermal signal based on the beat notes received from the photodetector for gas measurements. The PTS system can also be based on a core-cladding-mode interference detection scheme and generates the core mode and cladding mode simultaneously for the probe laser in the waveguide.

Mid-infrared photothermal heterodyne imaging (MIR-PHI) techniques described herein overcome the diffraction limit of traditional MIR imaging and uses visible photodiodes as detectors. MIR-PHI experiments are shown that achieve high sensitivity, sub-diffraction limit spatial resolution, and high acquisition speed. Sensitive, affordable, and widely applicable, photothermal imaging techniques described herein can serve as a useful imaging tool for biological systems and other submicron-scale applications.

An inspection system (1600), a lithography apparatus, and an inspection method are provided. The inspection system (1600) includes an illumination system (1602), a detection system (1606), and processing circuitry (1622). The illumination system generates a first illumination beam (1610) at a first wavelength and a second illumination beam (1618) at a second wavelength. The first wavelength is different from the second wavelength. The illumination system irradiates an object (1612) simultaneously with the first illumination beam and the second illumination beam. The detection system receives radiation (1620) scattered by a particle (1624) present at a surface (1626) of the object at the first wavelength. The detection system generates a detection signal. The processing circuitry determines a characteristic of the particle based on the detection signal.

A microscopic object detection system includes a collecting kit and a detection device. The collecting kit has a thin film for converting light into heat and is configured to be capable of holding a sample on the thin film. The detection device detects a plurality of microscopic objects in the sample by collecting the plurality of microscopic objects dispersed in the sample with the collecting kit. The detection device includes a laser module, an optical receiver, and a controller. The laser module emits a laser beam with which the collecting kit is irradiated. The optical receiver detects the laser beam from the sample held by the collecting kit and outputs a detection signal thereof. The controller calculates an amount of the plurality of microscopic objects collected in the sample based on a change of the detection signal over time.

A non-destructive method for chemical imaging with ˜1 nm to 10 μm spatial resolution (depending on the type of heat source) without sample preparation and in a non-contact manner. In one embodiment, a sample undergoes photo-thermal heating using an IR laser and the resulting increase in thermal emissions is measured with either an IR detector or a laser probe having a visible laser reflected from the sample. In another embodiment, the infrared laser is replaced with a focused electron or ion source while the thermal emission is collected in the same manner as with the infrared heating. The achievable spatial resolution of this embodiment is in the 1-50 nm range.

System for performing chemical spectroscopy on samples from the scale of nanometers to millimeters or more with a multifunctional platform combining analytical and imaging techniques including dual beam photo-thermal spectroscopy with confocal microscopy, Raman spectroscopy, fluorescence detection, various vacuum analytical techniques and/or mass spectrometry. In embodiments described herein, the light beams of a dual-beam system are used for heating and sensing.

A method and an interferometric device for spectroscopically or spectrometrically examining a sample, comprising: a) generating a laser beam having a wavelength, b) splitting the laser beam into a measurement beam and a reference beam, c) interacting the sample with the measurement beam, d) interacting a reference with the reference beam, e) overlaying the measurement beam and the reference beam, f) detecting a first output beam, g) detecting a second output beam, h) forming a differential signal between the first output signal and the second output signal, i) controlling the differential signal to a predefined target value, j) determining a refractive index of the sample from the adjustment of the phase difference between the measurement beam and the reference beam, k) repeating steps a) to j) for additional wavelengths of the laser beam.

Systems and methods are provided for performing thermophotonic imaging using cross-correlation and subsequent time-gated truncation. Photothermal radiation is detected with an infrared camera while exciting a sample with a chirped set of incident optical pulses and time-dependent photothermal signal data is processed using a method that involves performing cross-correlation and subsequent time-gated truncation. The post-cross-correlation truncation method results in depth-resolved images with axial and lateral resolution beyond the well-known thermal-diffusion-length-limited, depth-integrated nature of conventional imaging modalities. An axially resolved photothermal image sequence can be obtained, capable of reconstructing three-dimensional visualizations of photothermal features in wide classes of materials.