Nuvonyx CEO to speak at Marketplace Seminar
The potential for high-power laser diodes to displace conventional material processing technologies will be the focus of a talk given by Mark Zediker, president and CEO of Nuvonyx, at the 2002 Laser and Optoelectronics Marketplace Seminar in January. Zediker will also discuss the future of diode-laser technology and how it will challenge today's lasers.
Hosted by Laser Focus World and Strategies Unlimited (Mountain View, CA), the Marketplace Seminar provides business leaders, investors, and technology analysts with a close look at the laser and optoelectronics industries and where each market segment is heading. Presentations at the 2002 seminar include Laser Focus World's annual review of global laser markets, an overview of business and technology trends in the industrial laser marketplace, and focused discussions of other key markets.
Highlights include the keynote address, "Semiconductor Capital Equipment Trends and Outlook," by Dan Tracy, senior market analyst at SEMI (Semiconductor Equipment and Materials International; San Jose, CA); a review of tunable diode-laser product and market trends in optical communications by Tom Hausken, senior analyst at Strategies Unlimited; an overview of the worldwide fiberoptic-communications infrastructure by Richard Mack, vice president and general manager of market research firm KMI (Newport, RI); and an analysis of the medical-laser business and emerging technology and application trends by Robert Grant, executive vice president of the surgical business at Lumenis (Santa Clara, CA).
The seminar will take place Monday, Jan. 21, during the Photonics West meeting in San Jose, CA. For more information, contact the Registration Coordinator: phone 603-891-9267; fax 603-891-9490; email firstname.lastname@example.org.
Ultrafast laser writes interleaver with 400-GHz channel spacing
Researchers at Translume (Ann Arbor, MI) have built an interferometric photonic device using laser direct-write technology. This technology uses a focused beam from an ultrafast laser to locally change the index of refraction in a transparent dielectric. By scanning the beam through the material, waveguides may be written in any desired geometry, including in three dimensions.
The prototype device is an interleaver (an unbalanced Mach-Zehnder interferometer) with 400-GHz channel spacing. It consists of two approximately 50:50 directional couplers, the arms of which are connected by two waveguides of differing lengths. The device was written in a 1 x 5-cm area 300 µm below the surface of a glass block using 120-fs, 100-nJ pulses from a Ti:sapphire laser. At 800 nm the waveguides exhibit a mode field diameter of 4 µm and are polarization-maintaining. Extension from 800 nm to telecommunications wavelengths should be straightforward since the waveguides work out to wavelengths longer than 1600 nm, say the researchers. The contrast between adjacent channels is 10 dB. Current work includes developing the process to produce devices with much tighter specifications and using slightly modified device designs to produce photonic switches. Contact Phillipe Bado at email@example.com.
Miniature magneto-optic trap holds and transports BEC
Bose-Einstein condensates (BECs) of atoms cooled to almost absolute zero have been used to slow and stop light. Researchers at the Max Planck Institut für Quantenoptik and Sektion Physik der Ludwig Maxmilians Universität (Munich, Germany) have now simplified the production of BECs using a magneto-optical technique that includes a microscopic magnetic trap on a semiconductor chip.
A trapping potential is created by adding the field produced by lithographically made conductors and an external bias. Laser-cooled rubidium atoms 1 mm away from the chip surface are drawn into the magnetic trap, which holds the atoms for periods as long as 5 s. Magnetic manipulation of the atom cloud produces a BEC within a time as short as 0.7 s and with a lifetime of up to 1.3 s. Proper patterning of the lithographic wire structures permits not only the creation of BECs, but their transportation via periodically modulated currents. A so-called magnetic conveyor belt moves a BEC over a distance of 1.6 mm parallel to the chip surface; the cloud can then be released to undergo free motion. Contact Jakob Reichel at firstname.lastname@example.org.
All-dielectric micromirrors minimize temperature deformation
At the annual meeting of the IEEE Lasers and Electro-Optics Society (LEOS) in San Diego, CA, last month, researchers from the University of Minnesota (Minneapolis, MN) described the design and testing of all-dielectric micromirrors that maintained their shape within 0.016 of a wavelength at 633 nm over a temperature range of 30°C. The piston-type, electrostatic, polysilicon micromirrors were about 2.5 µm thick and ranged in diameter from 50 to 300 µm. Four polysilicon beam supports connected each mirror to the surrounding substrate above a 2.0-µm air gap. The mirrors were coated with a high-reflectivity, distributed Bragg reflector (DBR) stack of silicon dioxide/silicon nitride (SiO2/SiN) pairs beneath a yttrium trioxide/silicon dioxide (Y2O3/SiO2) pair that provided thermal compensation, because the thermal expansion coefficients of Y2O3 and SiO2 were respectively higher and lower than the DBR stack. Mirrors were tested over a temperature range of 21°C to 58°C and thermal deformation was evaluated using a thermally controlled chip mount with a phase-measurement interference microscope. Contact Joseph Talghader at email@example.com.
Gallium-diffused sapphire waveguides may lead to lasers
Because of its broad emission spectrum, titanium-doped sapphire is a common tunable laser medium. When in waveguide form, however, the material does not have low pump-power thresholds as a result of large modal spot sizes. Scientists at the University of Southampton's Optoelectronics Research Centre (Southampton, England) have successfully replaced the titanium with gallium to fabricate gallium-diffused waveguides in sapphire, which may lead to low-threshold broadly tunable waveguide lasers. Diffusion of 60- to 200-nm-thick films of gallium was performed on eight samples of sapphire 1 cm2 and 0.5 mm thick at 1600°C for times ranging from 6 to 16 h. Nearfield intensity profiles of the guided modes were measured at wavelengths from 488 to 850 nm, showing a surface-index elevation of up to 0.6 x 10-2.
Samples with greater diffusion depths exhibited cutoff at longer wavelengths and had substantially smaller modal spot sizes. At 488 nm, a mode size of 1.4 µm was obtained for one sample, significantly smaller than that obtained for titanium-diffused sapphire waveguides. Such small mode sizes allow low pump-power thresholds, opening up the possibility of miniature, tunable, and pulsed laser sources for microscopy, spectroscopy, and sensing. Contact Vasilis Apostolopoulos at firstname.lastname@example.org.
Quantum-well infrared detector sees three bands at once
Scientists at the University of Florida (Gainesville, FL), the Ballistic Missile Defense Organization (Washington, DC), and IQE Inc. (Bethlehem, PA) have developed a quantum-well infrared photodetector that simultaneously detects three bands in the mid-and long-wavelength infrared regions. The device contains three stacks and has detection bandwidths with full-widths at half-maximum at 5.9 to 7.0, 9.1 to 11.2, and 12.2 to 16.9 µm. Indium gallium arsenide quantum wells were used in all three stacks. The wavelength ranges were chosen to coincide with the major portion or entire range of the three atmospheric blocking bands that include the water, ozone, and carbon dioxide bands. Peak responsivities for the three bands were measured to be 0.13 A/W at 6.5 µm and 40 K, 1.08 A/W at 10.1 µm and 40 K, and 0.42 A/W at 15.1 µm and 30 K. Possible uses for the detector include exoatmospheric interceptors, space-based surveillance, and satellite mapping. Contact Sheng Li at email@example.com.
Modelocked fiber laser yields all-optical clock division
According to a presentation at the annual meeting of the IEEE Lasers and Electro-Optics Society (LEOS) in San Diego, CA, last month, researchers at Princeton University (Princeton, NJ) and Tsinghua University (Beijing, China) have overcome the problem of very short carrier lifetimes for high-speed input signals in all-optical clock division for optical time-division multiplexing. They achieved all-optical clock division at 10 GHz using a modelocked fiber laser and a semiconductor optical amplifier (SOA) with a slow carrier recovery time by building a numerical model of the modelocked semiconductor fiber laser and using a terahertz optical asymmetric demultiplexer (TOAD) as the optical modulator to perform clock division. In addition to the TOAD, the model included a bandpass filter, an erbium-doped fiber amplifier, and a 10:90 coupler. A 10-GHz erbium-doped fiber ring laser served as the pulse source, providing 11-ps-wide input pulses at 12 mW average optical power. Average optical power within the laser cavity was 6 mW and the SOA gain recovery time was 600 ps with a bias current of 120 mA. Contact Lei Xu at Leixu@ee.princeton.edu.
Nearfield microscope uses millimeter-wave radiation
Using millimeter-wave radiation as the illumination source, researchers at Sogang University (Seoul, Korea) are using nearfield microscopic techniques to obtain images at very high subwavelength resolution. The microscope's resonant-waveguide probe contains a sharp metallic tip that couples energy into and out of the waveguide; measurements of the resonant-frequency shift and the change of the quality factor in the nearfield regime allow the researchers to acquire images of oxide thin-films on magnesium oxide substrates with spatial resolutions to better than 2 µm.
The operating frequency ranged from 30 to 39 GHz, with the source being a mechanically tuned Gunn oscillator. A fundamental mode was excited in the waveguide resonator and the transmitted wave analyzed using a crystal detector and a spectrum analyzer. The input signal was modulated for synchronous detection. Objects placed near the probe changed the reflection coefficient in the probe tip. An image was taken at 36 GHz of a patterned film with a linewidth of 20 µm and a thickness of 50 nm. The radius of the probe tip was 5 µm and the sample-tip separation 2 µm. The 2-µm resolution could be increased by decreasing the tip radius, say the researchers. Contact Kiejin Lee at firstname.lastname@example.org.
Indium gallium nitride LED shines in green and blue
Researchers at Brown University (Providence, RI), Agilent Technologies (Palo Alto, CA), and Lumileds Lighting (San Jose, CA) have fabricated a monolithic dual-wavelength indium gallium nitride light-emitting diode (LED) and demonstrated its use for spectral fingerprinting of fluorescent molecular dyes. The blue- and green-emitting LED may someday also be useful in full-color displays, reducing the distinct LED elements in such a display from three to two.
The proof-of-concept device contains two electrically independent quantum wells of differing indium composition built into a single vertical heterostructure. A gallium nitride tunnel junction separates the two active regions, which emit at 470 and 535 nm. The two emitting regions can be controlled independently in any desired time sequence up to speeds of almost 100 MHz. For the demonstration, the researchers mixed two types of dye-doped microspheres in an aqueous solution, with each dye approximately matching one of the LED wavelengths in absorption. The time sequence of the LEDs was used to gate a photodetector that captured the fluorescence signals. Such operations could potentially be done at high speed. Contact Arto Nurmikko at email@example.com.