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The relative optical gains at three near infrared wavelengths (1550 nm, 1064 nm, and 980 nm) were achieved in NaYF4: Er3+, Yb3+ nanoparticle-doped SU-8 waveguides when using two low-cost light-emitting diodes (LEDs) instead of traditional 980 nm semiconductor laser as pump source. The polymer waveguides were fabricated by one-step photolithography process. The fluorescence bands around 1550 nm and 1000 nm wavelengths due to the 4I13/2 → 4I15/2 transition of Er3+ ions and 2F5/2 → 2F7/2 transition of Yb3+ ions were observed under the excitation of 405 nm and 520 nm LEDs. By using the vertical top pumping mode of LEDs, the relative gains of 4.2 dB, 1.7 dB, and 2.1 dB at 1550 nm, 1064 nm, and 980 nm wavelengths were achieved, respectively, on a 10-mm-long waveguide.

InGaN/GaN multiple quantum well-solar cells with different barrier thicknesses have been comparatively studied, and it is demonstrated that a thinner barrier facilitates the transport of photogenerated carriers. Meanwhile, an abnormal but regular staircase-like I-V curve is observed. The induction factors and microscopic physical process relevant to this abnormal feature are analyzed in detail, which is found closely related to the inadequate internal field and special epitaxial structure. Furthermore, the formation conditions of I-V curves with various types of inflections are also proposed. This work provides insight into the origin of device problems, which can be applicable to other types of solar cells.

An electrically pumped wavelength-tunable InGaN quantum dot (QD) based microcavity (MC) lighter emitter with a large tuning range of 129 nm was demonstrated. The multi-mode emission spectrum was tuned by injected current from 564 nm (yellow-green) to 435 nm (violet). The MC light emitter is featured with a double dielectric distributed Bragg reflector structure and a copper substrate fabricated using substrate transfer and laser lift off techniques. By utilizing an InGaN QD active layer with a tunable broad emission spectrum and a Fabry-Perot cavity which allows multi-longitudinal mode resonating, the emission spectrum could be tuned among several particular cavity modes, which are decided by the gain enhancement factor. In addition, both the enhancement and suppression of MC emission modes caused by the gain enhancement factor were observed in a single MC device. As the first electrically driven III-V nitride semiconductor based tunable MC light emitter with a tuning range of 129 nm, the device is promis...

Continuous wave (CW) lasing of electrically injected GaN-based vertical cavity surface emitting lasers (VCSELs) was achieved at room temperature. First, a high quality factor (Q) VCSEL-structured device with very narrow linewidth of 0.12 nm, corresponding to a Q-value of 3570 was obtained through two-step substrate transfer technique. However, poor heat dissipation ability prevented the device from lasing. Based on the high-Q resonant cavity design, we further fabricated vertical-structured VCSELs through metal bonding technique on Si substrate. CW lasing from vertical-structured VCSELs was observed with threshold current of density of 1.2 kA/cm2 and lasing linewidth of about 0.20 nm.