Current Issue : April - June Volume : 2012 Issue Number : 2 Articles : 7 Articles
We report a novel ultrabroadband high-energy femtosecond laser to be built in our laboratory. A 7-femtosecond pulse is firstly\r\nstretched by an eight-pass offner stretcher with a chirp rate 15 ps/nm, and then energy-amplified by a two-stage optical parametric\r\nchirped pulse amplification (OPCPA). The first stage as preamplification with three pieces of BBO crystals provides the majority\r\nof the energy gain. At the second stage, a YCOB crystal with the aperture of 50mm is used instead of the KDP crystal as the\r\ngain medium to ensure the shortest pulse. After the completion, the laser will deliver about 8 J with pulse duration of about\r\n10 femtoseconds, which should be beneficial to the attosecond pulse generation and other ultrafast experiments....
Red VCSELs offer the benefits of improved performance and lower power consumption for medical and industrial sensing, faster\r\nprinting and scanning, and lower cost, higher speed interconnects based upon plastic optical fiber (POF). However, materials\r\nchallenges make it more difficult to achieve the desired performance than at the well-developed wavelength of 850 nm. This paper\r\nwill describe the state of the art of red VCSEL performance and the results of development efforts to achieve improved output power\r\nand a broader temperature range of operation. It will also provide examples of the applications of red VCSELs and the benefits\r\nthey offer. In addition, the packaging flexibility offered by VCSELs, and some examples of non-Hermetic package demonstrations\r\nwill be discussed. Some of the red VCSEL performance demonstrations include output power of 14mWCWat room temperature,\r\na record maximum temperature of 115?C for CW operation at an emission wavelength of 689 nm, time to 1% failure at room\r\ntemperature of approximately 200,000 hours, lifetime in a 50?C, 85% humidity environment in excess of 3500 hours, digital data\r\nrate of 3 Gbps, and peak pulsed array power of greater than 100mW....
The porous silicon (PSi) layers were formed on p-type silicon (Si) wafer. The six samples were anodised electrically with 30 mA/cm2\r\nfixed current density for different etching times. The structural, optical, and thermal properties of porous silicon on silicon\r\nsubstrates were investigated by photoluminescence (PL), photoacoustic spectroscopy (PAS), and UV-Vis-NIR spectrophotometer.\r\nThe thickness and porosity of the layers were measured using the gravimetric method. The band gap of the samples was measured\r\nthrough the photoluminescence (PL) peak and absorption spectra, then they were compared. It shows that band gap value increases\r\nby raising the porosity. Photoacoustic spectroscopy (PAS) was carried out for measuring the thermal diffusivity (TD) of the\r\nsamples....
We present a controlling technique of microporous structure by laser irradiation during self-organization process. Selforganization\r\nprocess is fabrication method of microstructure. Polymer solution was dropped on the substrate at high humid\r\ncondition. Water in air appears dropping air temperature below the dew point. The honeycomb structure with regularly aligned\r\npores on the film was fabricated by attaching water droplets onto the solution surface. We demonstrate that it was possible to\r\nprevent forming pores at the region of laser irradiation and flat surface was fabricated. We also demonstrated that a combination\r\nstructure with two pore sizes and flat surface was produced by a single laser-pulse irradiation. Our method is a unique\r\nmicrofabrication processing technique that combines the advantages of bottom-up and top-down techniques. This method is a\r\npromising technique that can be applied to produce for photonic crystals, biological cell culturing, surface science and electronics\r\nfields, and so forth....
The optical properties of afterglow nanoparticles were successfully improved by the addition of polyethylene glycol (PEG) to an\r\nafterglow colloidal solution. Afterglow nanoparticlesââ?¬â?Sr2MgSi2O7: Eu2+, Dy3+ââ?¬â?were prepared by laser ablation in liquid. The\r\nquantum yields and the decay curves were measured by a fluorescence spectrophotometer. An increase in the amount of PEG\r\nadded to the solution increased the quantum yield of the nanoparticles and improved the afterglow property in the initial portion\r\nof the decay curve. However, the afterglow property did not change after a substantial amount of time had passed. The afterglow\r\nnanoparticles were capped with PEG molecules, and surface defects of the nanoparticles were passivated, which decreased the\r\noptical properties....
We review the design, fabrication, and performance of photonic crystal vertical cavity surface emitting lasers (VCSELs). Using\na periodic pattern of etched holes in the top facet of the VCSEL, the optical cavity can be designed to support the fundamental\nmode only. The electrical confinement is independently defined by proton implantation or oxide confinement. By control of the\nrefractive index and loss created by the photonic crystal, operation in the Gaussian mode can be insured, independent of the lasing\nwavelength....
We report the monolithic integration, fabrication, and electrooptical properties of AlGaAs-GaAs-based transceiver (TRx) chips\r\nfor 850nm wavelength optical links with data rates of multiple Gbit/s. Using a single butt-coupled multimode fiber (MMF),\r\nlow-cost bidirectional communication in half- and even full-duplex mode is demonstrated. Two design concepts are presented,\r\nbased on a vertical-cavity surface-emitting laser (VCSEL) and a monolithically integrated p-doped-intrinsic-n-doped (PIN) or\r\nmetal-semiconductor-metal (MSM) photodetector. Whereas the VCSEL-PIN photodiode (PD) chips are used for high-speed\r\nbidirectional data transmission over 62.5 and 50 �µm core diameter MMFs, MSM TRx chips are employed for 100 or 200 �µm\r\nlarge-area fibers. Such a monolithic transceiver design based on a well-established material system and avoiding the use of external\r\nfiber coupling optics is well suited for inexpensive and compact optical interconnects over distances of a few hundred meters.\r\nStandard MMF networks can thus be upgraded using high-speed VCSEL-PIN transceiver chips which are capable to handle data\r\nrates of up to 10 Gbit/s....
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