Thermo-optical Media Research Articles

The Penrose process in nonlinear optics

Penrose process is a mechanism by which energy may be extracted from the rotation of a Kerr black hole. The goal of this Perspective is to describe the elements that combine to allow a tabletop nonlinear optics experiment involving laser propagation in a medium to provide a versatile platform for elucidating the intimate details of the Penrose process. Key elements include propagation in a thermo-optic medium viewed as a photon fluid, rotating black hole geometries in a photon superfluid, and the Zel'dovich effect, and we highlight connections to the work of Roger Penrose throughout. In addition, we point out how the Penrose process has led to the notion of geometry-induced phase-matching in nonlinear optics, thereby highlighting the synergy between the fields of nonlinear optics and analog black holes.

Robust optical physical unclonable function using disordered photonic integrated circuits

Abstract Physical unclonable function (PUF) has emerged as a promising and important security primitive for use in modern systems and devices, due to their increasingly embedded, distributed, unsupervised, and physically exposed nature. However, optical PUFs based on speckle patterns, chaos, or ‘strong’ disorder are so far notoriously sensitive to probing and/or environmental variations. Here we report an optical PUF designed for robustness against fluctuations in optical angular/spatial alignment, polarization, and temperature. This is achieved using an integrated quasicrystal interferometer (QCI) which sensitively probes disorder while: (1) ensuring all modes are engineered to exhibit approximately the same confinement factor in the predominant thermo-optic medium (e. g. silicon), and (2) constraining the transverse spatial-mode and polarization degrees of freedom. This demonstration unveils a new means for amplifying and harnessing the effects of ‘weak’ disorder in photonics and is an important and enabling step toward new generations of optics-enabled hardware and information security devices.

Vortex revivals and Fermi-Pasta-Ulam-Tsingou recurrence.

We study the self-trapped vortex-ring eigenstates of the two-dimensional Schrödinger equation with focusing Poisson and cubic nonlinearities. For each value of the topological charge l, there is a family of solutions depending on a parameter that can be understood as the relative importance of the cubic term. We analyze the perturbative stability of the solutions and simulate the fate of the unstable ones. For l=1 and l=2, there is an interval of the family of eigenstates for which the initial profile breaks apart but subsequently reconstructs itself, a process that can be interpreted as a nontrivial nonlinear oscillation between the vortex and an azimuthon. This revival provides a compelling realization of a recurrence of the Fermi-Pasta-Ulam-Tsingou type. Outside this interval, the vortices can be stable (for small cubic terms) or unstable and nonrecurrent (for large cubic terms). We argue that there is a crossover between these regimes that resembles a strong stochasticity threshold. For l≥3, all solutions are unstable and nonrecurrent. Finally, we comment on the possible experimental implementation of this phenomenon in the context of nonlinear laser beam propagation in thermo-optical media.

Spatial solitons in thermo-optical media from the nonlinear Schrödinger-Poisson equation and dark-matter analogs

We analyze theoretically the Schrodinger-Poisson equation in two transverse dimensions in the presence of a Kerr term. The model describes the nonlinear propagation of optical beams in thermooptical media and can be regarded as an analogue system for a self-gravitating self-interacting wave. We compute numerically the family of radially symmetric ground state bright stationary solutions for focusing and defocusing local nonlinearity, keeping in both cases a focusing nonlocal nonlinearity. We also analyze excited states and oscillations induced by fixing the temperature at the borders of the material. We provide simulations of soliton interactions, drawing analogies with the dynamics of galactic cores in the scalar field dark matter scenario.

A parallel-multipoint fiber-optic temperature sensor based on Fresnel reflection

A parallel-multipoint fiber-optic temperature sensor for monitoring ambient temperature with a measured temperature resolution of approximately 0.03 °C is presented. The sensor relies on the temperature-dependent Fresnel reflection from each interface between a sensing fiber tip and a thermo-optic medium. An arrayed waveguide grating is used to achieve wavelength-division multiplexed-multipoint sensing. Applying the relative-intensity technique, the errors resulting from fluctuation of the light source and other influences of the environment are eliminated, and the stability for long time measurement can be improved.

A Quasi-Distributed Fiber-Optic Temperature Sensor With a Resolution of 0.07 $^{\circ}$C Based on Fresnel Reflection

A quasi-distributed fiber-optic temperature sensor for monitoring ambient temperature with a measured temperature resolution of approximately 0.07degC is presented. The sensor operates based on temperature-dependent Fresnel reflection from each interface between a distributed fiber tip and a thermooptic medium, and on the parallel demultiplexing of an arrayed waveguide grating. Thin-film filters are utilized to achieve wavelength-division multiplexing-distributed sensing. Good long-term stability and negligible channel crosstalk between two adjacent sensing heads with a wavelength spacing of 0.8 nm are experimentally achieved. Such a sensor would have biomedical and industrial applications where accurate measurements of temperatures and their locations are essential.

Fiber-Optic Temperature Sensor Based on Single Mode Fused Fiber Coupler

This paper reports a fiber-optic temperature sensor using a single mode fused fiber coupler incorporating a thermo-optic external medium. The spectral transmission was altered by changing the refractive index of the external thermo-optic medium. A theoretical and experimental investigation was carried out with the aim of achieving high sensitivity. The measured sensitivity for the environmental temperature was as high as -1.5 nm/℃.

Dynamics of a coupled double-cavity optical interference filter

The model of a coupled double-cavity optical interference filter consisting of three mirror layers and two one-wavelength cavities is developed. The transmission response of the coupled double-cavity filter containing absorbing thermo-optical media is predicted, when a laser pulse is incident on the filter. Pulse narrowing and pulse regeneration are observed for a restricted range of frequencies and intensities.

An optically coupled thermal imager

A novel scheme for thermal imaging is proposed, using a thermal IR detector whose temperature is sensed using a thermo-optic property, and the image is read electronically using a conventional television chip. As with other thermal IR detectors, the image is mechanically chopped, and the difference between fields calculated electronically. The particular scheme discussed uses a liquid crystal as the thermo-optic medium. Calculations of signal and measurements of noise are presented to deduce what the performance of such a thermal imager would be.