Optical vortex solitons in a defocusing saturable medium are analyzed in the framework of the (2 1 1)-dimensional generalized nonlinear Schrödinger equation. Stationary, radially symmetric localized solutions with nonvanishing asymptotics and a phase singularity (vortex solitons) are found numerically for the varying saturation parameter. Relaxation of some localized initial profiles (e.g., vor...

We first demonstrate a novel high-speed and highpower p-i-n photodiode with a cutoff wavelength at ∼2.5 μm. This device is composed of a partially depleted p-type Ga0.8In0.2As0.16Sb0.84 photo-absorption layer grown on GaSb substrate in order to enhance its speed and saturation power performance. With proper passivation processes, a low dark current (∼0.7 μA) and wide (6 GHz) optical-to-electric...

Understanding tumor vascular dynamics through parameters such as blood flow and oxygenation can yield insight into tumor biology and therapeutic response. Hyperspectral microscopy enables optical detection of hemoglobin saturation or blood velocity by either acquiring multiple images that are spectrally distinct or by rapid acquisition at a single wavelength over time. However, the serial acqui...

We present a brief overview of recent experimental and theoretical results on optical vortex solitons (in particular, those recently obtained at the Australian National University). Special attention is paid to a direct comparison between the experimental data on the structure and motion of vortex solitons created as localized structures in a diffracting Gaussian beam and the theory based on th...

Stimulated Raman backscattering in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers because plasma is fully broken down and withstands extremely high electric fields. Plasma also has unique nonlinear optical properties that allow simultaneous compression of optical pulses to ultra-short durations. However, current measured efficiencies are limited to ...

Photoacoustic microscopy (PAM) does not rely on contrast agent to image the optical absorption contrast in biological tissue. It is uniquely suited for measuring several tissue physiological parameters, such as hemoglobin oxygen saturation, that would otherwise remain challenging. Researchers are designing new clinical diagnostic tools and multimodal microscopic systems around PAM to fully unle...

Electro-optical imaging sensors are widely distributed and used for many different tasks. Due to technical improvements, their pixel size has been steadily decreasing, resulting in a reduced saturation capacity. As a consequence, this progress makes them susceptible to intense point light sources. Developments in laser technology have led to very compact and powerful laser sources of any wavele...

Group Members: Fanpeng Kong, Yubo Qin, Zhengyu Yang and Zhongtian Lin Advisor: Prof. Laleh Najafizadeh Introduction The aim of this project is to design a wearable pulse oximeter which is capable of measuring the heart-rate and blood’s oxygen saturation. The project employs wearable electronics. The project consists of three main parts: 1) sensor design, which includes the optical transceiver u...

Objective: Thrombosis of a site of anastomosis in microsurgical free tissue transfer can result in tissue necrosis. To salvage potentially failing free flap, various methods of monitoring the viability of tissue have been described. We report a novel method of monitoring free flaps using near-infrared spectroscopy. Methods: After microsurgical operation, we monitored the regional oxygen saturat...

We present the design, fabrication, and characterization of III-nitride quantum-well waveguides optimized for nonlinear-optical switching via intersubband transitions. A dielectric structure consisting of an AlN lower cladding and a GaN cap layer allows minimizing the propagation losses while maintaining a large modal overlap with the quantum-well active layer. A strong nonlinear saturation of ...