Chip-scale Full-Stokes Spectropolarimeter in Silicon Photonic Circuits

Wavelength-dependent polarization state of light carries crucial information about light-matter interactions. However, its measurement is limited to bulky, energy-consuming devices, which prohibits many modern, portable applications. Here, we propose and demonstrate a chip-scale spectropolarimeter implemented using a CMOS-compatible silicon photonics technology. Four compact Vernier microresonator spectrometers are monolithically integrated with a broadband polarimeter consisting of a 2D nanophotonic antenna and a polarimetric circuit to achieve full-Stokes spectropolarimetric analysis. The proposed device offers a solid-state spectropolarimetry solution with a small footprint of 1*0.6 mm2 and low power consumption of 360 mW}. Full-Stokes spectral detection across a broad spectral range of 50 nm with a resolution of 1~nm is demonstrated in characterizing a material possessing structural chirality. The proposed device may enable a broader application of spectropolarimetry in the fields ranging from biomedical diagnostics and chemical analysis to observational astronomy.Comment: 14 pages, 12 figures, uses jabbrv.st

Chip-scale full-Stokes spectropolarimeter in silicon photonic circuits

Wavelength-dependent polarization state of light carries crucial information about light-matter interactions. However, its measurement is limited to bulky, high energy-consuming devices, which prohibits many modern, portable applications. Here, we propose and demonstrate a chip-scale spectropolarimeter implemented using a complementary metal oxide semiconductor (CMOS) compatible silicon photonics technology. Four compact Vernier microresonator spectrometers are monolithically integrated with a broadband polarimeter consisting of a 2D nanophotonic antenna and a polarimetric circuit to achieve full-Stokes spectropolarimetric analysis. The proposed device oers a solid-state spectropolarimetry solution with a small footprint of 1 ⇥ 0.6 mm2 and low power consumption of 360 mW. Full-Stokes spectral detection across a broad spectral range of 50 nm with a resolution of 1 nm is demonstrated in characterizing a material possessing structural chirality. The proposed device may enable a broader application of spectropolarimetry in the fields ranging from biomedical diagnostics and chemical analysis to observational astronomy

Optically induced dynamics in nematic liquid crystals : the role of twist deformation and asymmetry

We present a theoretical study of optically induced dynamics in a homeotropic nematic liquid crystal excited at normal incidence. By retaining the first symmetric and antisymmetric reorientation modes, the dynamical equations are reduced to a four-dimensional problem. The main advantage of this minimal approach is to emphasize the role of twisted mode and asymmetry of the light-induced molecular reorientation in a manner suitable for a clear physical interpretation. Theoretical results are compared with experiments in the particular case of circularly polarized light beams to show the physical origin of mode competition and of the breakdown of chiral and longitudinal symmetry. The model successfully describes previous experimental studies such as time-dependent three-dimensional molecular dynamics, light-induced stabilized helical reorientation, and in-plane precession regime in achiral nematics. While a recent experiment has revealed a new spatiotemporal transition, the model succeeds to describe all the features of such a bifurcation pointing out anew the importance of asymmetry. Finally, the first quantitative description of the appearance of a giant mirrorless optical bistability when twisted reorientation modes are excited is demonstrated. A qualitative physical interpretation is suggested for all these phenome

Optically induced dynamics in nematic liquid crystals : the role of finite beam size

We report on the influence of a finite beam size on the molecular reorientation dynamics when a nematic liquid crystal film is excited by a laser beam. We present experimental evidence of a new class of nonlinear dynamics when the excitation is a Gaussian shaped, circularly polarized laser beam at normal incidence. Various nonlinear regimes, periodic, quasiperiodic, intermittent, and possibly chaotic, are observed. A physical interpretation based on walk-off effects is proposed and its implications on current research in the field are discusse

A camera trap to reveal the obscure world of the arctic subnivean ecology

Subnivean life is an important part of the Arctic ecosystem but it has been little explored. Long, harsh winters in addition to remoteness have made direct studies in these hardly accessible areas very expensive and extremely difficult. To tackle this problem, a low-power autonomous camera system (called ArcÇav) is developed for monitoring small mammals beneath the snow in the Canadian Arctic. ArcÇav is composed of several components, including a digital camera, a single board computer, a microcontroller board, and a motion detection sensor. A limited energy source, very cold temperatures, darkness, and a very long recording period (several months) are major challenges that ArcÇav is designed to deal with. The performance of the developed system is evaluated in a real situation in the High Arctic. The field results show that ArcÇav can function well for an extended period of time on a battery at very low temperatures during the arctic winters. To the best of our knowledge, this is the first time that life under snow has been filmed by a camera trap in the Arctic during winter. ArcÇav equips ecologists with a new means to explore and study subnivean life remotely. These observations can provide a foundation to answer some of questions that have puzzled animal ecologists for decades

Optical design challenges of subnivean camera trapping under extreme arctic conditions

Camera trapping is widely used in different ecological studies and is particularly important for remote locations and extreme environments. However, the application of camera traps in arctic regions remains very limited. One of the challenges is the formation of hoar on the lens of cameras. In this article we propose a solution to address this problem by changing the camera parameters and its position in order to optimize the camera trap for long-term subnivean deployment in the Canadian Arctic. Preliminary field tests show that this approach allows tracking lemmings in the frozen environment without natural light nor external electrical power supply, where the direct observations are impossible for the most part of the year. We obtained the first videos of lemmings under the snow during the arctic winter. Extending the observational network of the newly designed camera traps will help to better understand lemming population dynamics. The demonstrated approach is also promising for other polar application

Emotional burnout characteristics of Lithuanian judo coaches in aspect with gender and age

Objective of the thesis - to disclose the specificities of emotional exhaustion in judo coaches. Study methods 1. Analysis of literature; 2. Questionnaires; 3. Mathematical statistics. Conclusions 1. The results obtain from the use of BQC methods showed that the incidence of emotional exhaustion is more common in male coaches if compared to female coaches, but the difference is not significant statistically (p>0,05). The results of exhaustion degree obtained from the use of BQ methods were statistically significant (p>0,05). The majority of the respondents showed the exhaustion degree below the moderate degree; high exhaustion degree was found neither in male nor in female coaches. Female coaches exhibited better abilities of coping with exhaustion than male coaches, but these data are not significant statistically (p>0,05). 2. The emotional exhaustion results obtained from the use of BQC methods have not revealed any statistically significant differences from the point of view of age (p>0,05). Almost one fifth of younger respondents and one third of senior respondents were experiencing emotional exhaustion. Distribution of the degrees of emotional exhaustion within the respondents is not significant statistically, but most often the respondents of both the groups experience low degree of exhaustion; the rare incidence of moderate degree of exhaustion was found and there was no any high degree of exhaustion found in the respondents (p>0,05). The results obtained through the use of BO methods disclosed that the couches below 35 years are able to cope with emotional exhaustion better, but the differences are statistically insignificant (p>0,05). 3. The study results revealed statistically important links: moderate links have been found between the degree of emotional exhaustion and the ability to cope with it (p<0,01); statistically reliable negative links: weak links have been found between the gender and emotional exhaustion (p<0,05); strong links have been found between emotional exhaustion and the degree of emotional exhaustion (p<0,01) and between emotional exhaustion and the ability to cope with it (p<0,01)