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Biofeedback (BF) is expected not only as a means for gaining control of bodily processes to increase relaxation, relieve pain and improve health, but also to develop and improve the brain's body control function. The aim of the biofeedback training (BFT) is to promote the recovery and the development of physical dysfunctions under consciousness. A BF instrument has three tasks. First is to monitor (in some way) a physiological process of interest. Second is to measure (quantify) what is monitored. Third is to present what is monitored or measured as meaningful information. One technique for non-invasive measurement of brain activity that has been developed in recent years is brain functional imaging using near-infrared spectroscopy (NIRS). Compared to other techniques of measurement of brain activity, NIRS is a low-restraint and non-invasive measuring technique. In addition, it enables a user to take electrophysiological measurements such as Electromyography and Electrocardiography during training activity or other movements. In recent years, NIRS has a high profile for investigations of the relationship between physical control and brain function.Here, we investigated the connection between BFT and local cerebral blood flow, by performing cranial NIRS with simultaneous electromyogram (EMG), recording from the rectus femoris muscle. Our results suggest that We have succeeded in findings of the nonlinearity for hemodynamics in the cerebral blood flow on the frontal lobe during the muscle contraction and the post-rest.

We have investigated the use of nanopillar structures on high indium content InGaN amber multiple quantum well (MQW) samples to enhance the emission efficiency. A significant emission enhancement was observed which can be attributed to the enhancement of internal quantum efficiency and light extraction efficiency. The size-dependent strain relaxation effect was characterized by photoluminescence, Raman spectroscopy and time-resolved photoluminescence measurements. In addition, the light extraction efficiency of different MQW samples was studied by finite-different time-domain simulations. Compared to the as-grown sample, the nanopillar amber MQW sample with a diameter of 300 nm has demonstrated an emission enhancement by a factor of 23.8.

Nanopillar InGaN/GaN green light-emitting diode (LED) arrays were fabricated by self-assembled Au nanoparticles patterning and dry etching process. Structure size and density of the nanopillar arrays have been modified by varying the Au film thickness in the nanopatterning process. Fabricated nanopillar LEDs have been characterized by both room temperature and temperature-dependent photoluminescence measurements. A considerable internal quantum efficiency enhancement was achieved which is attributed to the suppressed quantum confined Stark effect derived from the internal strain relaxation. Meanwhile light extraction efficiency can also be enhanced significantly due to the increased light scattering at nanopillar sidewall. Compared to the planar LED, the nanopillar LED demonstrates the greatest external quantum efficiency enhancement by a factor of 4.08. It is believed that this nanopillar fabrication method can serve as an effective approach to increase the luminescence efficiency of LEDs.

We report internal quantum efficiency enhancement of thin p-GaN green quantumwell structure using self-assembled Ag nanoparticles. Temperature dependent photoluminescence measurements are conducted to determine the internal quantum efficiency. The impact of excitation power density on the enhancement factor is investigated. We obtain an internal quantum efficiency enhancement by a factor of 2.3 at 756 W/cm2 , and a factor of 8.1 at 1 W/cm2 . A Purcell enhancement up to a factor of 26 is estimated by fitting the experimental results to a theoretical model for the efficiency enhancement factor.

We fabricate a multi-colored quantum-well structure as a prototype towards monolithic white light-emitting diodes, and modify the emission intensities of different colors by introducing dielectric and Ag nanoparticle coating.

High-efficiency garnium nitride (GaN) based blue light-emitting diode (LED) paves the way for solid statelighting to take the place of the conventional incandescent bulbs and fluorescent light tubes.Compared to the traditional light sources, solid state lighting is more efficient, more flexible in spectral design, more compact etc. TheIII-nitride (GaN, InNetc.) semiconductors are attracting a lot of research effort because the combination of both could emit light with wavelength range from UV to infrared. Basically one material platform could provide all the solutions to light sources.However huge amount of material development is needed before high efficiency devices are achieved. Among them,one effort area is the so called ‘greengap’, i.e. low efficiency for green color LEDs due to the large piezoelectric field in the quantum wells (QWs) when the In composition is high. From the material growth point of view, the efficiency of green LED is being improved by growing the GaInN material on non-polar or semi-polar surface of sapphire substrate. In parallel with the material growth effort, surface plasmons are implemented by taking use of the interactionbetween metals and active areas to increase the efficiency.In this paper, our work on using silver (Ag) nanoparticles (NPs ) to enhance the efficiency of the green LEDs is reviewed. Both random and periodic Ag nanoparticles are studied. The random Ag nanoparticles are formed by thermal annealing of thin films.Periodic Ag nanoparticles are formed through nanosphere lithography. For both cases, emission enhancement is demonstrated. For periodic Ag nanoparicles, aphotoluminescence enhancement of 2.7 is observed with a nanodisk diameter of 330 nm.It is found that an optimalpitch exists for a given particle size.For the random Ag nanoparticles,low temperature photoluminescence (LTPL) was measured and internal quantum efficiency (IQE) enhancement by thesurface plasmons was derived. Excitation power dependence of IQE enhanceme

Surface plasmonics from metal nanoparticles have been demonstrated as an effective way of improving the performance of low-efficiency light emitters. However, reducing the inherent losses of the metal nanoparticles remains a challenge. Here we study the enhancement properties by Ag nanoparticles for InGaN/GaN quantum-well structures. By using a thin SiN dielectric layer between Ag and GaN we manage to modify and improve surface plasmon coupling effects, and we attribute this to the improved scattering of the nanoparticles at the quantum-well emission wavelength. The results are interpreted using numerical simulations, where absorption and scattering cross-sections are studied for different sized particles on GaN and GaN/SiN substrates.

Ag nanodisks are fabricated on GaN-based LED to enhance emission efficiency. Nanosphere lithography is used to obtain a periodic nano-structure, and a photoluminescence enhancement of 2.7 is reported with Ag nanodisk diameter of 330 nm.