Optimizational 6-bit all-optical quantization with soliton self-frequency shift and pre-chirp spectral compression techniques based on photonic crystal fiber

In this paper, we optimize a proposed all-optical quantization scheme based on soliton self-frequency shift(SSFS)and pre-chirp spectral compression techniques. A 10m-long high-nonlinear photonic crystal fiber(PCF) is used as an SSFS medium relevant to the power of the sampled optical pulses. Furthermore, a 10m-long dispersion flattened hybrid cladding hexagonal-octagonal PCF(6/8-PCF) is utilized as a spectral compression medium to further enhance the resolution. Simulation results show that 6-bit quantization resolution is still obtained when a 100m-long dispersion-increasing fiber(DIF)is replaced by a 6/8-PCF in spectral compression module.

Improved perceptually non-uniform spectral compression for robust speech recognition

According to the decline of recognition rate of speech recognition system in the noise environments, an improved perceptually non-uniform spectral compression feature extraction algorithm is put forward in this paper. This method can realize an effective compression of the speech signals and make the training and recognition environments more matching, so the recognition rate can be improved in the noise environments. By experimenting on the intelligent wheelchair platform, the result shows that the algorithm can effectively enhance the robustness of speech recognition, and ensure the recognition rate in the noise environments.

Computational Spectral Imaging Based on Compressive Sensing

Spectral imaging is an important tool for a wide variety of applications. We present a technique for spectral imaging using computational imaging pattern based on compressive sensing （CS）. The spectral and spatial infor- mation is simultaneously obtained using a fiber spectrometer and the spatial light modulation without mechanical scanning. The method allows high-speed, stable, and sub sampling acquisition of spectral data from specimens. The relationship between sampling rate and image quality is discussed and two CS algorithms are compared.

New low-rank optimization model and algorithms for spectral compressed sensing

In this paper, we investigate the recovery of an undamped spectrally sparse signal and its spectral components from a set of regularly spaced samples within the framework of spectral compressed sensing and super-resolution. We show that the existing Hankel-based optimization methods suffer from the fundamental limitation that the prior knowledge of undampedness cannot be exploited. We propose a new low-rank optimization model partially inspired by forward-backward processing for line spectral estimation and show its capability to restrict the spectral poles to the unit circle. We present convex relaxation approaches with the model and show their provable accuracy and robustness to bounded and sparse noise. All our results are generalized from one-dimensional to arbitrary-dimensional spectral compressed sensing. Numerical simulations are provided to corroborate our analysis and show the efficiency of our model and the advantageous performance of our approach in terms of accuracy and resolution compared with the state-of-the-art Hankel and atomic norm methods.

Robust and rapidly tunable light source for SRS/CARS microscopy with low-intensity noise

We present a fully automated laser system with low-intensity noise for coherent Raman scattering microscopy.The robust two-color system is pumped by a solid-state oscillator,which provides Stokes pulses fixed at 1043 nm.The tunable pump pulses of 750 to 950 nm are generated by a frequency-doubled fiberfeedback femtosecond optical parametric oscillator.The resulting pulse duration of 1.2 ps provides a viable compromise between optimal coherent Raman scattering signal and the necessary spectral resolution.Thus a spectral range of 1015 to 3695 cm−1 with spectral resolution of<13 cm−1 can be addressed.

Synchronization-free all-solid-state laser system for stimulated Raman scattering microscopy

We introduce an extremely simple and highly stable system for stimulated Raman scattering(SRS)microscopy.An 8-W,450-fs Yb:KGW bulk oscillator with 41 MHz repetition rate pumps an optical parametric amplifier,which is seeded by a cw tunable external cavity diode laser.The output radiation is frequency doubled in a long PPLN crystal and generates 1.5-ps long narrowband pump pulses that are tunable between 760 and 820 nm with 450 mW average power.Part of the oscillator output is sent through an etalon and creates Stokes pulses with 100 mW average power and 1.7 ps duration.We demonstrate SRS microscopy at a 30-μs pixel dwell time with high chemical contrast,signal-to-noise ratio in excess of 45 and no need for balanced detection,thanks to the favorable noise properties of the bulk solid-state system.Cw seeding intrinsically ensures low spectral drift.We discuss its application to chemical contrast microscopy of freshly prepared plant tissue sections at different vibrational bands.