Optics (physics.optics)

Abstract: Self-compression is a simple method to achieve ultrashort and ultraintense pulses. By solving a modified nonlinear Schrodinger equation considering the fifth-order susceptibility, it is found that self-compression appeared even in normally dispersive media owing to the negative fifth-order susceptibility inducing a mass of negative frequency chirp. Furthermore, negatively pre-chirped pulses help to achieve pulse self-compression at lower input peak intensity which will avoid the damage of media. The optimized-choosing of pre-chirp, input intensity and length of media are numerically analyzed. Proof-of-principle experiments successfully prove the above theoretical findings. It is expected that petawatt laser pulses with 25 fs/15 fs transform limited pulse duration can be self-compressed to about 10.7 fs/8.8 fs in normally dispersive media such as fused silica glass plates.

Abstract: We provide an insight into the origin of the phenomena reported 40 years ago by Kerker, Wang and Giles (Journal of the Optical Society of America, 73, 6, pp. 765-767, (1983)). We show that the impedance and refractive index matching conditions, discussed in Sections II and IV of the seminal paper, are intimately related with space-time symmetries. We derive our results starting from the theory of representations of the Poincar\'e group, as it is the theory on which one of the most elemental descriptions of electromagnetic waves is based. We show that fundamental features of electromagnetic waves in material environments can be derived from group theoretical arguments. In particular, we identify the Casimir invariants of $P_{\scriptscriptstyle{{3,1}}}$ subgroup as the magnitudes which describe the nature of monochromatic electromagnetic waves propagating in matter. Finally, we show that the emergence of the Kerker phenomena is associated with the conservation of such Casimir invariants in piecewise homogeneous media.

Abstract: Whereas electromagnetic surface waves are confined to a planar interface between two media, line waves exist at the one-dimensional interface between three materials. Here we derive a non-local integral equation for computing the properties of line waves, valid for surfaces characterised in terms of a general tensorial impedance. We find a good approximation -- in many cases -- is to approximate this as a local differential equation, where line waves are one-dimensional analogues of surface plasmons bound to a spatially dispersive metal. For anisotropic surfaces we find the oscillating decay of recently discovered `ghost' line waves can be explained in terms of an effective gauge field induced by the surface anisotropy. These findings are validated using finite element simulations.

Abstract: Dark modes represent a class of forbidden transitions or transitions with weak dipole moments between energy states. Due to their low transition probability, it is difficult to realize their interaction with light, let alone achieve the strong interaction of the modes with the photons in a cavity. However, by mutual coupling with a bright mode, the strong interaction of dark modes with photons is possible. This type of mediated interaction is widely investigated in the metamaterials community and is known under the term electromagnetically induced transparency (EIT). Here, we report strong coupling between a plasmonic dark mode of an EIT-like metamaterial with the photons of a 1D photonic crystal cavity in the terahertz frequency range. The coupling between the dark mode and the cavity photons is mediated by a plasmonic bright mode, which is proven by the observation of a frequency splitting which depends on the strength of the inductive interaction between the plasmon bright and dark modes of the EIT-like metamaterial. In addition, since the plasmonic dark mode strongly couples with the cavity dark mode, we observes four polariton modes. The frequency splitting by interaction of the four modes (plasmonic bright and dark mode and the two eigenmodes of the photonic cavity) can be reproduced in the framework of a model of four coupled harmonic oscillators.

Abstract: Femtosecond laser filament-induced plasma spectroscopy (FIPS) demonstrates great potentials in the remote sensing for identifying atmospheric pollutant molecules. Due to the widespread aerosols in atmosphere, the remote detection based on FIPS would be affected from both the excitation and the propagation of fingerprint fluorescence, which still remain elusive. Here the physical model of filament-induced aerosol fluorescence is established to reveal the combined effect of Mie scattering and amplification spontaneous emission, which is then proved by the experimental results, the dependence of the backward fluorescence on the interaction length between filament and aerosols. These findings provide an insight into the complicated aerosol effect in the overall physical process of FIPS including propagation, excitation and emission, paving the way to its practical application in atmospheric remote sensing.

Abstract: Power amplifier is becoming a critical component for integrated photonics as the integrated devices try to carve out a niche in the world of real-world applications of photonics. That is because the signal generated from an integrated device severely lacks in power which is due mainly to the small size which, although gives size and weight advantage, limits the energy storage capacity of an integrated device due to the small volume, causing it to rely on its bench-top counterpart for signal amplification downstream. Therefore, an integrated high-power signal booster can play a major role by replacing these large solid-state and fiber-based benchtop systems. For decades, large mode area (LMA) technology has played a disruptive role by increasing the signal power and energy by orders of magnitude in the fiber-based lasers and amplifiers. Thanks to the capability of LMA fiber to support significantly larger optical modes the energy storage and handling capability has significantly increased. Such an LMA device on an integrated platform can play an important role for high power applications. In this work, we demonstrate LMA waveguide based CMOS compatible watt-class power amplifier with an on-chip output power reaching ~ 1W within a footprint of ~4mm2.The power achieved is comparable and even surpasses many fiber-based amplifiers. We believe this work opens up opportunities for integrated photonics to find real world application on-par with its benchtop counterpart.