This PDF file contains the front matter associated with SPIE Proceedings Volume 12323, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

We theoretically study the generation of a Kerr frequency combs in a cylindrical microresonator with an effective radius variation. We investigate a model describing the propagation of the whispering gallery modes on the surface of an optical fiber coupled to a source. We also discusses the details of the numerical scheme and the effect of numerical dispersion on the nonlinear generation of axial eigenmodes.

Compact microresonator-based frequency comb sources are perspective elements of modern photonic technologies. They attract even more interest after the integrated device was demonstrated. The main disadvantage of the Kerr frequency combs is said to be the comparatively low generation power. However, this problem is not studied quite well. Previous studies concerned its dependence on the microresonator FSR, input power and coupling separately, expecting pump-to-comb efficiencies no more than five percents. Usually it is stated that the threshold power should be reduced to provide lower necessary pump and larger soliton existence range. However, the problem is quite complex as coupling also induce the changes into the loaded quality factor, threshold power and even the number of comb lines. Also more than 20% efficiency was demonstrated recently in the self-injection locking regime. Here we present the more comprehensive analysis of the comb generation efficiency optimization and show the theoretical way to reach the limit of 100%.

The optical feedback in random distributed feedback Raman fiber lasers is due to extremely weak Rayleigh backscattering, nevertheless it is capable of forming localized spectral modes at the generation threshold. Here we present experimental time-resolved observation of such ultra-narrow spectral modes, proving the presence of cascade Brillouin scattering during the generation. We realized a two-band optical heterodyning measurement system that allows studying the evolution of two arbitrary separated spectral regions with microsecond temporal and of-megahertz spectral resolution. Studying the occurrence rate for cascade Brillouin scattering, we found that it plays an important role in shaping the generation.

As one of the most promising optical nonlinear material, AlGaAs has several advantages such as high second and third order nonlinear coefficients, freedom of material engineering, potential of full quantum photonic system on chip (SOC) including pump laser. In this paper, we estimate the photon pair generation and second harmonic generation (SHG) by an AlGaAs Bragg Rreflection waveguide (BRW) which design and manufactured on GaAs substrate.

Single-frequency microlasers and photonic generation of microwave signal with a fast tuning are highly in demand for lots of applications, including high-resolution spectroscopy, precision metrology, coherent communication, and so on. Design and fabrication of narrow-linewidth microlasers and low-phase-noise microwave signal are challenging. Here, we fabricated high-Q erbium ion doped lithium niobate microcavities for single frequency lasing through simultaneous excitation of high-Q polygon modes at both pump and laser wavelengths. Tunable single-mode microlasers with linewidth as narrow as 454 Hz was demonstrated. Moreover, photonic generation of low-phase-noise microwave signals were synthesized from dual-wavelength microlasers on single active LNOI microdisks. The dual-wavelength microlasers were generated from high-Q nearly degenerate polygon modes with spatial intensity distributions almost the same but a -phase difference. Due to the suppression of the gain competition, dual-wavelength lasing and in turn the low noise microwave source are stable. The phase noise of the microwave signal was measured to -123 dBc/Hz.

This study designs an optimal optical 1 to 2 data distributor using a nonlinear optical effect within metal–insulator–metal plasmonic (MIM) waveguides based on the Mach–Zehnder interferometer. An optical source of 1550 nm and FDTD technique are utilized to design and simulate the proposed structure. The FDTD results are then validated using a MATLAB simulation of the design. The proposed design can be used in high-speed combinational circuits to distribute a given data to 2ⁿ users.

A theoretical model was proposed to simulate the broadband second harmonic generation (SHG) based on random quasiphase matching (RQPM) by Fourier transform mothed. A broadband SHG experiment system was built which could obtain the distribution of the SHG signal over a whole ZnSe sample. Both the simulated and experimental results demonstrated that the main feature of RQPM is the linear dependency of the SHG intensity with sample thickness.

The throughput of error correction is the main bottleneck of continuous variable quantum key distribution (CV-QKD) postprocessing. Implementing the decoder of low-density parity-check (LDPC) codes based on FPGA with limited precision can improve the decoding throughput significantly. However, the limited precision on FPGA results in the existence of residual error-bits after decoding, which lowers the secret key rate and restricts the application of high-rate real-time CVQKD system. In this paper, an efficient decoding scheme is proposed to erase the residual error-bits and decrease the frame errors rate (FER), where the decoding process into two stages and some values of initial Log Likelihood Ratio (LLR) are adjusted according to the proposed principles before starting the second-stage decoding. For the rates 0.2 and 0.1 LDPC codes, numerical results demonstrate that the proposed decoding scheme decreases the FER obviously and the throughputs of 152.47Mbps and 88.32Mbps are achieved, which can be applied to support high-speed CV-QKD system under transmission distance of 25km and 50km respectively.

Continuous-variable quantum key distribution (CV-QKD) offers the advantages of high secret key rates in metropolitan areas. Optimization of modulation variance is an efficient method to improve the secret key rate of CVQKD system. However, in practical CV-QKD system, inevitable slight parameter fluctuation could occur after the modification of modulation variance, and controlling the modulation variance with arbitrary accuracy is also difficult. In this paper, we propose a two-step optimization for practical CV-QKD. The first step is to determine the optimal working state by combining the modulation variance optimization with error correction matrix optimization. The second step is to optimize the rate-adaptive reconciliation parameters to compensate the loss of secret key rate caused by inaccuracy modulation variance. Our results show that the secret key rate can be improved by 17.8% in comparison to one-step optimization method. Our method can be conveniently applied to CV-QKD protocol with homodyne and heterodyne detection, which will pave the way to the deployment of high stable and high performance for CV-QKD.

The trusted phase noise model for continuous-variable quantum key distribution protocol with a real local oscillator (LLO CVQKD) has been established recently, which can lead to a better quantum key distribution (QKD) performance by moving part of the phase noise from the untrusted channel-added noise to the trusted detector-added noise. However, the calibration of the trusted phase noise is related to the intensity of the phase-reference pulse, which can be used by the eavesdropper to hack the QKD system. Here, we present a polarization attack scheme against the phase-reference pulse. In practical LLO CVQKD systems, only a part of the phase-reference pulses are used to measure and compensate for the polarization drift of the signal pulses due to the limitation of polarization measurement. We show that Eve can manipulate the polarization of the unmeasured part of the phase-reference pulses to control the trusted phase noise. Simulations show that improving the polarization measurement ratio to 100% or monitoring the phase-reference pulse intensity in real time is necessary to guarantee the security of the practical LLO CVQKD system.

In this paper, we experimentally demonstrate a 5 GBaud four-state continuous-variable quantum key distribution with digital signal processing. By employing a frequency- and polarization-multiplexing quantum key transceiver, the modulation noise and DAC quantization noise in quantum state preparation, the photo-leakage noise in co-fiber transmission, the detection noise and ADC quantization noise in polarization diversity detection can be effectively reduced for achieving an ultra-low level of excess noise. Moreover, the main polarization variation and phase noise can be accurately compensated by designing a precise digital compensation scheme including the pilot-assisted polarization and phase compensation algorithm and the data-assisted equalized compensation algorithm. Besides, the explicit asymptotic secure key rate is evaluated by using an improved semidefinite programming security analysis method, which achieves a 100 Mbps level of secure key rate within 10 km distance.

Due to many advantages of compact structure, high efficiency, good beam quality, etc., diode-pumped all-solid-state passively Q-switched lasers have a bright future in military, industrial processing, medicine, and other fields. At present, the relevant reports on diode-pumped all-solid-state passively Q-switched lasers mainly focus on the characteristics of the period-1 dynamic state, while there are few reports on the characteristics of other nonlinear dynamic states. In this work, we experimentally investigated the dynamic characteristics of a diode-pumped all-solid-state passively Q-switched Nd:LaMgAl₁₁O₁₉ laser by using a semiconductor saturable absorber mirror. The experimental results show that, under different absorbed pump power and cavity loss, the laser can display various dynamic states such as period-1, period-2, period-4, period-5, period-7, and chaotic pulsing states. Through changing the cavity loss, the laser goes through period- 1, period-2, period-4 to chaos, or period-1, period-5, period-7 to chaos.

In this paper, we present the research of the blinding attack on single photon avalanche diodes (SPAD) based on InGaAs structure which is used in quantum key distribution systems with modulated laser radiation. One of the variants of this attack is using continuous wave (CW) light but there is protection from it like monitoring of SPAD’s current. Thus, we use modulated CW radiations. Modulation allows us to establish parameters of blinding pulses. We studied the dependencies of the detector’s bias current on blinding pulse energy using different widths of light pulses in the range from 4ns to 20 ns than we applied various repetition rates which are 10 MHz, 5 MHz, 2.5 MHz, and 1MHz. Even we investigate this dependence using the not rectangular shape of pulses on repetition rates mentioned above.

In the present work, the formation of ultrashort pulses in a fiber laser resonator with the effect of slow saturable absorption and spectral filtering was studied. It has been shown that in a resonator with normal chromatic dispersion, the finite relaxation time of a saturable absorber leads to a spectral shift of the generated pulses with respect to the central length of the spectral filter. The numerical results are verified using two experimental laser sources: a ring fiber laser with a semiconductor saturable absrober mirror and a fiber laser with a nonlinear amplifying loop mirror. The results obtained are relevant for designing sources of ultrashort pulses in applications for which the spectral properties of radiation are crucial parameters.

Spectral properties of Raman fiber lasers with randomly distributed feedback well above generation threshold are mainly defined by nonlinear interactions in the fiber. The role of randomly distributed feedback hence is expected to be negligible, though this problem has not been investigated particularly. We numerically study spectral properties of a random fiber laser and a corresponding fiber amplifier with no feedback and emphasize the importance of Rayleigh backscattering: having marginal influence on generation efficiency, it affects the generation spectrum shape and width.