High doping concentrations of rare-earth ions in multi-component non-silica glass fibers yield high efficiency and high gain for laser operation, enabling us developing unique high-power fiber lasers at multiple wavelengths ranging from 1µm to 2µm.
We review nonlinear optical techniques to generate tunable few-cycle pulses. Optical parametric amplification allows producing few-cycle pulses tunable from the visible to the IR. Tunability is extended to the ultraviolet by sum-frequency generation. Difference frequency between ultrashort pulses generates broadband light in the mid-IR.
Optical frequency combs are used as a set of mutually coherently orthogonal signals to realize high speed signal processing. Here, we demonstrate novel comb sources, along with modulation and detection techniques that realize high speed sampling, arbitrary waveform generation and matched filtering functionality.
We differentiate the spacer-dependent peak shift in coupled and decoupled super absorbing metasurfaces based on magnetic resonance and interference mechanism, respectively, which was experimentally validated by low-cost structures fabricated by lithography-free processes.
High-speed vertical-cavity surface-emitting lasers (VCSELs) are important for optical data transmission applications. Modulation bandwidth for free-running VCSELs typically ranges from few to twenty GHz. An interesting discovery is that modulation bandwidth may be appreciably improved with coherently coupled arrays [1,2]. Recently we reported the ability to tune 2–1 phased, photonic crystal VCSEL...
We analyzed and fabricated a novel coupler which possesses wavelength flattened response and splitting ratio tuning capability. The fabricated coupler showed a flattened response to wavelength over 50 nm bandwidth and the coupling power to the cross port can be tuned from 10% to 70%.
An integrated tunable MSM PD based on Indium Tin Oxide (ITO) that is fabricated on Si and InP. Tuning is achieved by thermally controlling the bandgap of the semiconductor using a Nickel Chromium (NiCr) microheater.
The concept of transverse mode engineering in edge-emitting lasers with broadened waveguides based on coupled large optical cavity (CLOC) structures is presented. The CLOC lasers show improved beam quality and reduced divergence.
We investigated the effect of residual chromatic dispersion on phase-sensitive amplification of 20Gbaud 16QAM signals experimentally. We observed negligible impacts on amplification although the constellation is degraded in proportion to the amount of CD.
Direct modulation of membrane DFB laser was carried out. Small signal response showed −3dB bandwidth of 9.5 GHz at a bias current of 1 mA. This corresponds to modulation current efficiency factor of 9.8 GHz/mA½.
We investigate optical nanoantennas featuring asymmetrical stepped-junction structures. By breaking the symmetry of the conventional optical nanoantennas, the performance of them is improved in many aspects. Experiments have been conducted to validate the proposed design.
We focus on the use of the subwavelength crossed Ag grating top layer in the Ag/SiO2/Ag sandwich nanostructures as the ultrathin plasmonic super absorbers to efficiently enhance the light absorption by surface plasmon resonacne.
Single-mode lasing from broad area radial Bragg lasers is demonstrated experimentally. Numerical analysis as well as experimental characterization reveals surprising property of high mode discrimination at large angular modal numbers.
We present an electro-optic sensing system for power and electric field measurements at the W-band. An electro-optic probe was fabricated to be small enough to be inserted into a WR-10 waveguide to realize the endoscopic detection of fully guided electric fields. The intensity of the measured electric fields when propagating inside the field-calculable waveguide with respect to the applied power was...
Single photons are efficiently collected based on a tunable microfiber-coupled photonic crystal cavity with an embedded InAs quantum dot. 25% of total fiber collection efficiency is obtained. Tunability of the cavity and Purcell-enhanced spontaneous emission rate are also observed.
We experimentally and theoretically investigate microwave signal generation using a 1550nm VCSEL subject to two-frequency parallel optical injection. It is found that microwave signals can be generated outside the double injection locking region.
We present our recent development of fiber-optic endomicroscopy technology capable of performing nonlinear optical imaging of unstained biological tissues at histology resolution. Its potential applications for disease detection and basic research will also be discussed.
Nonlinear optical properties of gold nanoparticles (AuNPs) embedded ZnO thin films have been studied at 400 nm. While the AuNPs thin film shows the effect of saturable absorption, AuNPs embedded ZnO film exhibits the RSA behaviour.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.