A lighting device comprising first and second groups of solid state light emitters, which emit light having peak wavelength in ranges of from 430 nm to 480 nm, and first and second groups of lumiphors which emit light having dominant wavelength in the range of from 555 nm to 585 nm. In some embodiments, if current is supplied to a power line, a combination of (1) light exiting the lighting device which was emitted by the first group of emitters, and (2) light exiting the lighting device which was emitted by the first group of lumiphors would have a correlated color temperature which differs by at least 50 K from a correlated color temperature which would be emitted by a combination of (3) light exiting the lighting device which was emitted by the second group of emitters, and (4) light exiting the lighting device which was emitted by the second group of lumiphors.

Lighting device and lighting method

Transparent conducting oxides for electrode applications in light emitting and absorbing devices

The random laser represents a non-conventional laser whose feedback is mediated by random fluctuation of the dielectric constant in space. Depending on whether the feedback is intensity or field feedback, random lasers are classified into two categories: a random laser with incoherent and non-resonant feedback, and a random laser with coherent and resonant feedback. This paper reviews some of the latest developments in the latter, including experiments and theories on the 'classical' and 'quantum' type of random lasers with coherent feedback, the photon localization lasers. The quantum theories of random lasers are briefly introduced, followed by a discussion of the recent studies on the interplay between light localization and coherent amplification.

/pdf/review-on-latest-developments-in-random-lasers-with-coherent-599az1gmiy.pdf

Review on latest developments in random lasers with coherent feedback

There is provided a lighting device which emits light with an efficacy of at least 60 lumens per watt. The lighting device comprises at least one solid state light emitter (16), e.g, one or more light emitting diodes, and optionally further includes one or more lumiphor (35). In some embodiments, the output light is of a brightness of at least 300 lumens. In some embodiments, the output light has a CRI Ra of at least 90. Also, a method of lighting, comprising supplying electricity to a lighting device which emits light with an efficacy of at least 60 lumens per watt.

Lighting device and method of lighting

Recent advances in ultraviolet photodetectors

Nitride-based blue light emitting diodes (LEDs) with an n/sup +/-short period superlattice (SPS) tunnel contact layer and an indium tin oxide (ITO) transparent contact were fabricated. Compared with conventional nitride-based LEDs with Ni/Au upper contacts, it was found that we could achieve a 60% increase in electroluminescence (EL) intensity by using ITO upper contacts. However, it was also found that the lifetime of ITO LEDs were much shorter. Furthermore, it was found that we could achieve a longer lifetime and a smaller reverse leakage current (I/sub R/) by the deposition of a SiO/sub 2/ layer on top of the ITO LEDs.

Highly reliable nitride-based LEDs with SPS+ITO upper contacts

The optical and electrical properties of indium tin oxide (ITO)(60 nm), Ni(3.5 nm)/ITO(60 nm) and Ni(5 nm)/Au(5 nm) films were studied. It was found that the normalized transmittance of ITO and Ni/ITO films could reach 98.2% and 86.6% at 470 nm, which was much larger than that of the Ni/Au film. It was also found that both Ni/ITO and Ni/Au could form good ohmic contact on top of p-GaN. In contrast, ITO on p-GaN was electrically poor and non-ohmic. Nitride-based light-emitting diodes (LEDs) with these three p-contact layers were also fabricated. It was found that the LED forward voltage was 3.65, 3.26 and 3.24 V for the LEDs with ITO, Ni/ITO and Ni/Au p-contact layer, respectively. With a 20 mA current injection, it was also found that measured output power was 7.50, 6.59 and 5.26 mW for the LEDs with ITO, Ni/ITO and Ni/Au p-contact layer, respectively. Although the LED with ITO p-contact could provide the largest output intensity, its lifetime was the shortest due to severe heating effect.

http://focs.eng.uci.edu/papers%20for%20GaN/ITO%20contact/Lin%20InGaN%20GaN%20light%20emitting%20diodes%20with%20Ni%20Au,%20Ni%20ITO%20Solid%20state%20electronics%2047%20849%202003.pdf

InGaN/GaN light emitting diodes with Ni/Au, Ni/ITO and ITO p-type contacts

Nitride-based blue LEDs prepared on both patterned and conventional sapphire substrates were both fabricated It was found that although the EL peak positions of these two LEDs were about the same, the EL intensity of LED grown on patterned sapphire substrate was about 35% larger The maximum output power of LED grown on patterned sapphire substrate also occurred at higher injection current The reliability of LED grown on patterned sapphire substrate was also found to be better There improvements could all be attributed to the reduced dislocation density in the LEDs grown on patterned sapphire substrates

Nitride-based LEDs fabricated on patterned sapphire substrates

The optical and electrical properties of Ni(5 nm)-Au(5 nm) and Ni(3.5 nm)-indium tin oxide (ITO) (60 nm) films were studied. It was found that the normalized transmittance of Ni/ITO film could reach 87% at 470 nm, which was much larger than that of the Ni-Au film. It was also found that the specific contact resistance was 5 /spl times/ 10/sup -4/ /spl Omega/ /spl middot/ cm/sup 2/ and 1 /spl times/ 10/sup -3/ /spl Omega/ /spl middot/ cm/sup 2/, respectively, for Ni-Au and Ni/ITO on p-GaN. Furthermore, it was found that the 20 mA output power of light-emitting diode (LED) with Ni-Au p-contact layer was 5.26 mW. In contrast, the output power could reach 6.59 mW for the LED with Ni/ITO p-contact layer.

Nitride-based light-emitting diodes with Ni/ITO p-type ohmic contacts

The indium-tin-oxide [ITO(80 nm)] and Ni(5 nm)-Au(10 nm) films were separately deposited on glass substrates, p-GaN layers, n/sup +/-InGaN-GaN short-period-superlattice (SPS) structures, and nitride-based light-emitting diodes (LEDs). It was found that ITO on n/sup +/-SPS structure could provide us an extremely high transparency (i.e., 93.2% at 465 nm) and also a reasonably small specific contact resistance of 1.6/spl times/10/sup -3//spl Omega//spl middot/cm/sup 2/. Although the forward voltage which corresponds to 20-mA operating current for LED with ITO on n/sup +/-SPS upper contact was slightly higher than that of the LED with Ni-Au on n/sup +/-SPS upper contact, a 30% higher output intensity could still be achieved by using ITO on n/sup +/-SPS upper contact. Moreover, the output power of packaged LED with ITO was about twice as large as that of the other conventional Ni-Au LEDs.

C.S. Chang

Papers

Highly reliable nitride-based LEDs with SPS+ITO upper contacts

InGaN/GaN light emitting diodes with Ni/Au, Ni/ITO and ITO p-type contacts

Nitride-based LEDs fabricated on patterned sapphire substrates

Nitride-based light-emitting diodes with Ni/ITO p-type ohmic contacts

Nitride-based LEDs with an SPS tunneling contact Layer and an ITO transparent contact