Quartz Enhanced Photothermal Spectroscopy (QEPTS) is a technique, which enables developing gas sensors characterized by a broadband operational range and superb sensitivity. QEPTS relies on the thermoelastic effect induced by the illumination of the Quartz Tunning Fork (QTF) with a modulated laser radiation, which generates a piezoelectric signal. QTF excitation can occur at any wavelength, which is impossible to observe in e.g. semiconductor detectors. The sub-dollar cost of a QTF delivers simultaneously broadband and sensitive detection capability and significantly reduced costs of the sensor. Furthermore, as in majority of laser-based sensors, the sensitivity of QEPTS-based systems can be easily enhanced by increasing laser-gas interaction path length. This is typically realized by using multipass cells (MPCs), which significantly increase the sensor’s complexity and decrease its robustness. Instead of using MPCs, an Antiresonant Hollow-Core Fiber (ARHCF), designed for light transmission in more than one spectral band can be used as a long gas absorption cell, leading to the increase in the sensor’s performance while keeping its design simple. Here, we present a sensor utilizing a combination of an ARHCF-based absorption cell and the QEPTS. In the developed system the gas-filled ARHCF substitutes an MPC. The spectroscopic signal analysis relies on the use of a simple QTF with a resonance frequency of 32.744 kHz connected with a self-made, low-noise amplifier and an addition of a wavelength modulation spectroscopy – based signal retrieval scheme for sensor’s performance enhancement. The sensor enables simultaneous detection of acetylene and methane at parts-per-million by volume level sensitivity, targeting their absorption lines in the near- and mid-infrared. The results confirm excellent suitability of the ARHCF-aided QEPTS sensors for being employed as a versatile gas detectors. This research was funded by Narodowe Centrum Nauki (NCN), grant number UMO-2018/30/Q/ST3/00809.

Conventional measurement of bidirectional scattering distribution function (BSDF) and total transmittance (TT) is a serious topic. We have proposed a screen image synthesis (SIS) BSDF meter that provides high-speed and precise measurement. However, the measurement of TT using integrating sphere cannot offer a precise measurement. Therefore, we propose a calibration method that using SIS BSDF meter, responsivity of the integration sphere photometer and integration transmission power. It brings us not only precise BSDF function but precise TT measurement.

Multi-level phase encoding 2D signal is very important in the application of holographic data storage. However, conventional phase-shifting interferometry using addition reference beam suffers from the fluctuation in the phase stability, the phase-shifting, and the wavefront error of the reference beam. This paper proposes and demonstrates a pre-integral DFGSI with the utilization of a built-in phase-shifting function, to retrieve multi-level phase signals. This type of new interferometer will be helpful in optical testing in dynamic circumstances with a common path and without an additional reference wave.

In this talk, we will review the recent advances on KTN based fast speed KTN deflectors, including (1) how to achieve high quality beam steering, (2) how to achieve compact polarization independent beam steering, (3) how to reduce the driving voltage and power, (4) how to maximum the deflection range, and (5) how to minimize the heated generated from continuous beam steering.