arXiv subjects

Duk-Yong Choi

Publications and source records attributed to Duk-Yong Choi.

24 records · Page 2Linked to original sources

arXiv2017

Highly localized Brillouin scattering response in a photonic integrated circuit

The interaction of optical and acoustic waves via stimulated Brillouin scattering (SBS) has recently reached on-chip platforms, which has opened new fields of applications ranging from integrated microwave photonics and on-chip narrow-linewidth lasers, to phonon-based optical delay and signal processing schemes. Since SBS is an effect that scales exponentially with interaction length, on-chip implementation on a short length scale is challenging, requiring carefully designed waveguides with optimized opto-acoustic overlap. In this work, we use the principle of Brillouin optical correlation domain analysis (BOCDA) to locally measure the SBS spectrum with high spatial resolution of 800 μm and perform a distributed measurement of the Brillouin spectrum along a spiral waveguide in a photonic integrated circuit (PIC). This approach gives access to local opto-acoustic properties of the waveguides, including the Brillouin frequency shift (BFS) and linewidth, essential information for the further development of high quality photonic-phononic waveguides for SBS applications.

physics.optics↗

arXiv2016

Total absorption of visible light in ultra-thin weakly-absorbing semiconductor gratings

The perfect absorption of light in subwavelength thickness layers generally relies on exotic materials, metamaterials or thick metallic gratings. Here we demonstrate that total light absorption can be achieved in ultra-thin gratings composed of conventional materials, including relatively weakly-absorbing semiconductors, which are compatible with optoelectronic applications such as photodetectors and optical modulators. We fabricate a 41 nm thick antimony sulphide grating structure that has a measured absorptance of A = 99.3% at a visible wavelength of 591 nm, in excellent agreement with theory. We infer that the absorption within the grating is A = 98.7%, with only A = 0.6% within the silver mirror. A planar reference sample absorbs A = 7.7% at this wavelength.

physics.optics↗

arXiv2016

Observation of nonlinear thermal optical dynamics in a chalcogenide nanobeam cavity

We present a theoretical and experimental analysis of nonlinear thermo-optic effects in suspended chalcogenide glass nanobeam cavities. We measure the power dependent resonance peaks and characterise the dynamic nonlinear thermo-optic response of the cavity under modulated light input. Several distinct nonlinear characteristics are identified, including a modified spectral response containing periodic fringes, a critical wavelength jump and saturated time delay for modulation frequency faster than the thermal characteristic time. We reveal that the coupling to a parasitic Fabry-Perot cavity enables isolated thermal equilibrium states resulting in the discontinuous thermo-optic critical point.

physics.optics↗

arXiv2014

Low power, chip-based stimulated Brillouin scattering microwave photonic filter with ultrahigh selectivity

Highly selective and reconfigurable microwave filters are of great importance in radio-frequency signal processing. Microwave photonic (MWP) filters are of particular interest, as they offer flexible reconfiguration and an order of magnitude higher frequency tuning range than electronic filters. However, all MWP filters to date have been limited by trade-offs between key parameters such as tuning range, resolution, and suppression. This problem is exacerbated in the case of integrated MWP filters, blocking the path to compact, high performance filters. Here we show the first chip-based MWP band-stop filter with ultra-high suppression, high resolution in the MHz range, and 0-30 GHz frequency tuning. This record performance was achieved using an ultra-low Brillouin gain from a compact photonic chip and a novel approach of optical resonance-assisted RF signal cancellation. The results point to new ways of creating energy-efficient and reconfigurable integrated MWP signal processors for wireless communications and defence applications.

physics.optics↗

arXiv2014

Bi-photon spectral correlation measurements from a silicon nanowire in the quantum and classical regimes

The growing requirement for photon pairs with specific spectral correlations in quantum optics experiments has created a demand for fast, high resolution and accurate source characterization. A promising tool for such characterization uses the classical stimulated process, in which an additional seed laser stimulates photon generation yielding much higher count rates, as recently demonstrated for a $χ^{(2)}$ integrated source in A.~Eckstein \emph{et al.}, Laser Photon. Rev. \textbf{8}, L76 (2014). In this work we extend these results to $χ^{(3)}$ sources, demonstrating spectral correlation measurements via stimulated four-wave mixing for the first time in a integrated optical waveguide, namely a silicon nanowire. We directly confirm the speed-up due to higher count rates and demonstrate that additional resolution can be gained when compared to traditional coincidence measurements. As pump pulse duration can influence the degree of spectral entanglement, all of our measurements are taken for two different pump pulse widths. This allows us to confirm that the classical stimulated process correctly captures the degree of spectral entanglement regardless of pump pulse duration, and cements its place as an essential characterization method for the development of future quantum integrated devices.

physics.optics↗

arXiv2013

Narrow linewidth Brillouin laser based on chalcogenide photonic chip

We present the first demonstration of a narrow linewidth, waveguide-based Brillouin laser which is enabled by large Brillouin gain of a chalcogenide chip. The waveguides are equipped with vertical tapers for low loss coupling. Due to optical feedback for the Stokes wave, the lasing threshold is reduced to 360 mW, which is 5 times lower than the calculated single-pass Brillouin threshold for the same waveguide. The slope efficiency of the laser is found to be 30% and the linewidth of 100 kHz is measured using a self-heterodyne method.

physics.optics↗