Total Reflection Prism Research Articles

Inverted Transflection Spectroscopy of Live Cells Using Metallic Grating on Elevated Nanopillars.

Water absorption of mid-infrared (MIR) radiation severely limits the options for vibrational spectroscopy of the analytes-including live biological cells-that must be probed in aqueous environments. While internal reflection elements, such as attenuated total reflection prisms and metasurfaces, partially overcome this limitation, such devices have their own limitations: ATR prisms are difficult to integrate with multiwell cell culture workflows, while metasurfaces suffer from a limited spectral range and small penetration depth into analytes. In this work, we introduce an alternative live cell biosensing platform based on metallic nanogratings fabricated on top of elevated dielectric pillars. For the MIR wavelengths that are significantly longer than the grating period, reflection-based spectroscopy enables broadband sensing of the analytes inside the trenches separating the dielectric pillars. Because the depth of the analyte twice-traversed by the MIR light excludes the highly absorbing thick water layer above the grating, we refer to the technique as inverted transflection spectroscopy (ITS). The analytic power of ITS is established by measuring a wide range of protein concentrations in solution, with the limit of detection in the single-digit mg mL-1. The ability of ITS to interrogate live cells that naturally wrap themselves around the grating is used to characterize their adhesion kinetic.

An ultra-broadband frequency-agile terahertz perfect absorber with perturbed MoS2 plasmon modes.

Multidomain dynamic manipulations for terahertz (THz) absorbers usually necessitate the orchestrated actions of several active elements, inevitably complicating the structural design and elongating the modulation time. Herein, we utilize the coupling between the total reflection prism and electrically-driven MoS2 to activate a tight field confinement in a deep-subwavelength interlayer, ultimately achieving frequency-agile absorption adjustments only with a gate voltage. Theoretical and simulation analysis results indicate that the redistributed electric field and susceptible dielectric response are attributed to the limited spatial near-field perturbation of surface plasmon resonances. We also demonstrate that perturbed MoS2 plasmon modes promote the formation of dual-phase singularities, significantly suppressing the attenuation of the absorption amplitude as large-scale frequency shifts, thereby extending the relative tuning range (WRTR) to 175.4%. These findings offer an efficient approach for expanding the horizon of THz absorption applications that require ultra-broadband and swift-response capabilities.

Scale factor compensation technology of laser gyro with total reflection prism

针对全反射棱镜式激光陀螺标度因数随温度周期性变化的现象，根据矩阵光学方法研究了稳频状态下温度变化对环形激光面积的影响，获得了全反射棱镜式激光陀螺标度因数与稳频电压的关系，并得出光束偏移是引起标度因数随温度周期性变化的原因。根据标度因数与稳频电压的关系，建立了全反射棱镜式激光陀螺标度因数补偿模型，通过实验对比了补偿前后标度因数的非线性度。结果表明，根据该补偿模型对全反射棱镜式激光陀螺标度因数进行补偿，标度因数非线性度提高了一个数量级以上，对提高全反射棱镜式激光陀螺的性能具有一定的参考价值。

Quantitative detection of THz-ATR spectra of aqueous samples under strong-field terahertz wave

Owing to the characteristics of THz wave, the terahertz time-domain spectral (THz-TDS) system has potentials in the field of biological macromolecule detection. However, water with strong absorption effect on THz wave exists in most biological detection, so the research focus in this field is to study aqueous samples. In view of these, THz spectroscopy system has research value for qualitative and quantitative detection of α-lactose and its water-containing samples. This research used a THz-TDS system with LiNbO3 crystal to generate strong THz wave that was used to test 0.29mmol α-lactose samples with water content of 15μL-930μL by using attenuating total reflection (ATR) prism. The absorption peak at 0.53THz is detected, and with the increase of water content, the curve of absorption spectrum is observed to move up on the whole. This research has a guiding role for the test and improvement of water content limit in this field.

Effect of frequency stabilization on beam shift of total reflection prism laser gyro

For the phenomenon of degradation of the performance of total reflection prism laser gyro before and after reset jump, this paper investigates the effect of frequency stabilization on the beam shift of total reflection prism laser gyro using a matrix optics method, and proposes a method to calculate the beam shift with frequency stabilization. The numerical simulation and experimental results show that, unlike the beam shift characteristics caused by the prism temperature, the frequency stabilization additionally causes an approximately equal beam shift at each prism interface, and the shift is proportional to the frequency stabilization control amount. It is pointed out that the large abrupt change of beam propagation path before and after reset jump is the main reason for the degradation of total reflection prism laser gyro performance, and the frequency stabilization control method of reset jump once for each optical wavelength adjustment can effectively reduce the beam shift caused by frequency stabilization.

Dynamic full-field refractive index distribution measurements using total internal reflection terahertz digital holography

Massive usage scenarios prompt the prosperity of terahertz refractive index (THz RI) measurement methods. However, they are very difficult in measuring the full-field dynamical RI distributions of either solid samples without a priori thickness or liquid samples. In this study, we propose total internal reflection THz digital holography and apply it for measuring RI distributions for both solid and liquid samples dynamically. An RI measurement model is established based on an attenuated total reflection prism with a pitching angle. The pitching angle and the field of view can be numerically calculated from the spectrogram of the off-axis Fresnel hologram, which solves the adjustment of the visually opaque prism irradiated by the invisible THz beam. Full-field RI distributions of the droplets of solid-state soy wax and distilled water are obtained and compared with THz time-domain spectroscopy. The evaporation of an ethanol solution droplet is recorded, and the variation of the RI distribution at the sample–prism interface is quantitatively visualized with a temporal resolution of 10 Hz. The proposed method greatly expands the sample range for THz RI measurements and provides unprecedented insight into investigating spontaneous and dynamic THz phenomena.

Theoretical investigation of two-dimensional sub-wavelength structures fabricated by multi-beam surface plasmon interference lithography

In this study, multi-beam surface plasmon (SP) interference lithography was theoretically proposed and demonstrated to fabricate periodic two-dimensional sub-wavelength structures. The lithography structures were based on an attenuated total reflection prism used to excite the SPs using a 442 nm laser. Circular lattices with periods of 166 and 288 nm were successfully obtained via three- and six-beam SP interference lithography, respectively; these lattices exhibited an identical feature size of 96 nm. Square dot arrays with a 177 nm period and 88.5 nm spot size were obtained by four-beam SP interference lithography. The proposed lithography technology has a simple structure and is economical; further, it may provide an effective method for the fabrication of two-dimensional sub-wavelength structures.

Common path continuous terahertz reflection and attenuated total reflection imaging

Terahertz imaging technology is one of the candidate technologies for medical imaging. In particular, continuous terahertz reflection and attenuated total reflection imaging are expected to achieve rapid intraoperative imaging, which is hot research topic at present. In order to realize the rapid multi-dimensional and high-quality terahertz imaging detection of sample, it is necessary to study the common optical path continuous terahertz reflection/attenuated total reflection dual-mode imaging system based on point scanning. By using the Fresnel formula and the penetration depth formula of evanescent wave, the influence of imaging angle on the reflected signal and the penetration depth of attenuated total reflection are studied theoretically in this paper. The imaging angle of terahertz wave suitable for both reflection and attenuation total reflection imaging is obtained. Based on this, an isoscele total reflection prism with a base angle of 49° is designed. The dual-mode imaging of common optical path continuous terahertz reflection and attenuated total reflection is realized by quickly switching between reflection window and total reflection prism. The reflection and attenuation total reflection imaging modes have imaging resolutions of 400 μm and 500 μm, respectively. Continuous terahertz reflection and attenuated total reflection imaging are experimentally studied by using distilled water and pork as samples. The results show that the relative reflectance of the sample obtained in the attenuated total reflection imaging mode fluctuates within a range of 1%, and the image contrast is 9 times that of the reflection imaging mode. Moreover, attenuated total reflection imaging can effectively identify the sample with the length less than 1 mm. Thus, compared with reflection imaging, continuous terahertz attenuated total reflection imaging has the advantages of high image resolution, high image contrast and highr signal stability, and can accurately obtain the reflectivity of sample. The terahertz attenuated total reflection imaging technology is more helpful in achieving high sensitivity imaging of samples. By combining reflection and attenuated total reflection imaging modes, the advantages of different imaging modes can be compensated for and the performance of the imaging system can be further improved. This common path continuous terahertz reflection and attenuated total reflection dual mode imaging system is expected to achieve a high sensitivity detection of sample.

Dispersion-compensated polarization Sagnac interferometer with high imaging quality

Multistage diffraction of a dispersion-compensated polarization Sagnac interferometer (DCPSI) reduces the fringe visibility of interference fringes generated in a focal plane array, thereby leading to the poor quality of the reconstructed polarization images. In this paper, a double total reflection prism between the DCPSI and imaging lens is added to limit the effect of multistage diffraction and improve the imaging quality. First, the influence of multistage diffraction on the interference fringes and the ratio of fringe amplitude to the background was analyzed. Second, the range of angles of the two right angle prisms was calculated. Simulation and experiment were carried out to prove the superiority of the proposed method. Result shows that the ratio of fringe amplitude to the background increases from 1/5 to 1/3 and from 1/10 to 1/6 in simulation and experiment when a double total reflection prism structure is added respectively. This method can reduce the influence of multistage diffraction on interference fringes and improve the image quality of DCPSI effectively.

High-robustness intravascular photoacoustic endoscope with a hermetically sealed opto-sono capsule.

The prevailing open-structure intravascular photoacoustic (IVPA) endoscope emits a gradually deformed laser beam with exposed optical or acoustical components bearing pollution and damage in arterial lumen. Deformed laser beam scanning, which causes a low excitation efficiency and serious deterioration of the transverse resolution, is a current big obstacle to the application of photoacoustic endoscopy in intravascular imaging. Hence, the stable and reliable IVPA endoscope is indispensable. In this letter, we designed a high-robustness intravascular photoacoustic (HR-IVPA) endoscope with a hermetically sealed opto-sono capsule. The distal end of the opto-sono capsule was integrated with miniaturized optics, including a customized C-Lens and a customized total-reflection prism (TRP). The TRP was first applied to a side-viewing IVPA endoscope, featuring a high-throughput energy coupling efficiency of 90% and a cut-off free damage threshold. The optical path structure of the endoscope, optimized using optical simulation tools, overcame the ambiguous focus shift caused by chromatic dispersion and achieved a waist size of 20 µm as well as a focus depth of 4 mm in water at the wavelength of 1200 nm. The mass phantom experiments demonstrated that the HR-IVPA endoscope afforded repeatable IVPA images with a relatively constant signal-to-noise ratio (SNR) of about ∼41.8 dB and a transverse resolution of about ∼23 µm. The imaging experiments of the stent and lipid further demonstrated the robustness and validated the imaging ability of the HR-IVPA endoscope, which opens a new avenue for improving the endoscopic imaging capability, strengthening the credible detection of atherosclerotic cardiovascular disease.

A Method for Improving Light Intensity Stability of a Total Reflection Prism Laser Gyro Based on Series Correction and Feedforward Compensation

The instability of scale factor and null shift are closely related to the change of the light intensity of a total reflection prism laser gyro (TRPLG). To improve the light intensity stability, the light intensity stabilization principle of TRPLG was analyzed, and a mathematical model of light intensity stabilization system was established. Aiming at the problem that original system has a long adjustment time, a series correction method of adding a proportional integral differential (PID) link in the forward channel was adopted. According to the third-order optimal design, the original I-type third-order overdamped system was optimized to the new II-type third-order underdamped system, which ultimately improved the system's dynamic and steady-state performance. Feedforward compensation was used to introduce the light intensity disturbance during the longitudinal mode hopping into the closed-loop system, which realized the full compensation of the light intensity error and improved the light intensity characteristics during the longitudinal mode hopping. Combined with the above two methods, experimental results showed that the new system with feedforward compensation improved the light intensity stability by 32% at constant temperature and by 40% at variable temperature, with the TRPLG's bias stability improved by more than 16% at constant temperature and by 22% at variable temperature.

Поляриметрія анізотропного поверхневого шару на склі

Investigating the Stokes vector of light reflected from the surface of the optical glass, the presence of an anisotropic surface layer was established. The phase difference between radiation p- and s-components is revealed, which varies depending on the angle of incidence. This shows a weak anisotropy. Assuming that the anisotropic layer has an increased refractive index due to its chemical-mechanical treatment, it can be considered as some near-surface weakly guiding gradient burried waveguide. The possibility of coming radiation into such a planar waveguide using a coupling total reflection prism was investigated. The inspection showed a violation of the total internal reflection, unequal for p- and s-polarizations, which confirms the presence of the subsurface layer and its anisotropy. The absorption of radiation, which could be compared with the excitation of modes, is small. This is due to the properties of the prism material. Also, higher order modes are absorbed better. There is no significant angular dependence of the polarization degree of the output beam; however, it is higher in the case of s-polarization.

Kerr Electro-Optic Sensor for Electric Field in Large-Scale Oil–Pressboard Insulation Structure

The design of the oil–pressboard/paper insulation structure is the key to maintain the safe and reliable operation of power transformers, which mainly relies on simulation and verification test undertaken with simple or equivalent models, falling short of the physical entity verification undertaken in the large-scale structure. Based on the Kerr electro-optic effect and the optical fiber technology, a novel electric field measuring sensor was developed in this paper for the application test in the large-scale oil–pressboard structure. The sensor is contained of collimator, total reflection prism, coupler, and customized optical elements, whose appearance is a miniature capsule-shaped configuration. The key technical performance parameters of sensor were obtained, for instance, and the effect of imported sensor on the electric field under measurement is an average 1.17% reduction in intensity; the sensitivity of designed system is 162.84 V/mm under ac voltage and 40.43 V/mm under dc voltage. Under dc voltage, the measuring accuracy of the designed system is greater than 97.42%, while in the context of ac voltage, it could reach 97.14%. The application test was conducted to capture the dynamic process of the electric field in oil in the large-scale outlet device model, which has three uniformly spaced oil spacings divided by pressboards, under ac voltage, dc voltage, and polarity reversal voltage. The experimental results verify that the developed electric field sensor could be effectively and reliably applied in the large-scale oil–pressboard insulation, and it could be confidently inferred that the larger the scale of insulation structure, the better is the performance of sensor.

High Precision Compensation for a Total Reflection Prism Laser Gyro Bias in Consideration of High Frequency Oscillator Voltage.

Traditional compensation methods based on temperature-related parameters are not effective for complex total reflection prism laser gyro (TRPLG) bias variation. Because the high frequency oscillator voltage (UHFO) fundamentally affects the TRPLG bias, and the UHFO has a stronger correlation with the TRPLG bias when compared with the temperature, an introduction of UHFO into the TRPLG bias compensation can be evaluated. In consideration of the limitations of least squares (LS) regression and multivariate stepwise regression, we proposed a compensation method for TRPLG bias based on iterative re-weighted least squares support vector machine (IR-LSSVM) and compared with LS regression, stepwise regression, and LSSVM algorithm in large temperature cycling experiments. When temperature, slope of temperature variation, and UHFO were selected as inputs, the IR-LSSVM based on myriad weight function improved the TRPLG bias stability by 61.19% to reach the maximum and eliminated TRPLG bias drift. In addition, the UHFO proved to be the most important parameter in the process of TRPLG bias compensation; accordingly, it can alleviate the shortcomings of traditional compensation based on temperature-related parameters and can greatly improve the TRPLG bias stability.

Analysis on the characteristic of the optical axis perturbation in a total reflection prismring resonator.

The deduction of the augmented 5×5 matrix describing all the possible angular and decentration misalignment perturbation sources on a spherical prism plane during the refraction is presented in detail for the first time. Combining the augmented matrices and the condition of eigenmode self-consistency, the optical axis perturbation properties (described with the optical axis perturbation sensitivity factor SD1, ST1, SD2, and ST2) in a total reflection prism ring resonator are also analyzed. The singular points of the optical axis perturbation sensitivity factor are found at L/R=0.417 for the cases where the misalignments may originate from distinguished type of prisms P1 and P4 in the resonator, respectively. It is shown that the small errors of the prism can cause large optical axis disturbance in the position of the perturbed singular point and its nearby area, and the disturbance for the case where the misalignments originate from prism P1 is more violent than that of prism P4. With some upgrades to find and avoid the singularity of the optical axis in the total reflection prism ring resonator structure successfully, we expect this work will have great potential for designing and optimizing the structure of super-high-precision ring laser gyroscopes.

Analysis and Improvement of Frequency Stabilization Characteristics of a Total Reflection Prism Laser Gyro

To rectify the low accuracy of frequency stabilization for a total reflection prism laser gyro (TRPLG), a mathematical model for TRPLG frequency stabilization was established. Wavelet filtering was introduced into the phase-sensitive demodulation process, with a 6-scale decomposition for the alternating current (AC) signal of light intensity used with the db4 wavelet. Combined with soft threshold and forced denoising, the signal-to-noise ratio (SNR) of the phase-sensitive signal was improved by 23.3%, with the accuracy of the frequency stabilization improved by 0.5 orders of magnitude. Increasing the variable gain in the forward channel stabilized the dynamic performance of the frequency stabilization control system. A temperature-compensated feed-forward control system was used to achieve full compensation for the temperature-induced frequency stabilization error, which also improved the accuracy of the frequency stabilization by 1 order of magnitude. Combined with wavelet filtering and feed-forward compensation, the optimized frequency stabilization control system improved the accuracy of frequency stabilization by 1.5 orders of magnitude compared with the original frequency stabilization control system in the full temperature range, and it improved the gyro’s accuracy by more than 40%.

Characterization on the effect of linear stress birefringence in a total reflection prism ring resonator

Characterization on the effect of linear stress birefringence in a total reflection prism ring resonator

Fabrication of diamond-coated germanium ATR prisms for IR-spectroscopy

Monocrystalline germanium is considered a highly useful material for infrared optical applications due to its relatively low price, low toxicity and high optical transparency in the infrared spectral range (5500–870cm−1). However, it is limited by its low chemical, mechanical, and thermal stability. The thin film diamond coating can provide a mechanical protection of a Ge surface against scratching, chemical protection against solutions, and make a well-defined hydrophilic/hydrophobic surface. Here, we compare low temperature (250–400°C) diamond growth on Ge substrates and attenuated total reflection prisms, using a chemical vapor deposition in linear antenna microwave plasma and focused microwave plasma reactors. We show that by employing a thin amorphous silicon interlayer (20–30nm), a homogeneous diamond coating with no degradation of the Ge surface is achieved. The infrared spectroscopy of proteins adsorbed on the diamond coated Ge prism demonstrates usability and advantages in comparison with bare Si or Ge prisms and even with the diamond-coated Si prism.

One-way transmission through merging of magnetic defect state and optical Tamm states

Abstracts To achieve a new type of one-way transmission, we design a semi-infinite one-dimensional photonic crystal (PC) coated with a magneto-optical (MO) material film. In the surface of this structure there are merging states of MO defect state and optical Tamm state (OTS). We deduce the dispersion equation of the merging states basing on the Bloch theorem of periodic structures and transfer matrix method. There are two nonreciprocal dispersion curves of the merging states for k x and − k x , respectively. The positions of the merging states can be adjusted through changing the thickness of the MO film. With the use of the attenuated total reflection (ATR) prism coupling, we consider a one-way transmission based on a finite one-dimensional PC structure. The simulations by using a finite element method demonstrate the one-way transmission results.

Dynamical measurement of refractive index distribution using digital holographic interferometry based on total internal reflection

We present a method for dynamically measuring the refractive index distribution in a large range based on the combination of digital holographic interferometry and total internal reflection. A series of holograms, carrying the index information of mixed liquids adhered on a total reflection prism surface, are recorded with CCD during the diffusion process. Phase shift differences of the reflected light are reconstructed exploiting the principle of double-exposure holographic interferometry. According to the relationship between the reflection phase shift difference and the liquid index, two dimensional index distributions can be directly figured out, assuming that the index of air near the prism surface is constant. The proposed method can also be applied to measure the index of solid media and monitor the index variation during some chemical reaction processes.