We report here the photo-pumped lasing operation of GaAs1-xBix with low-temperature-dependent oscillation
wavelengths, and show future prospects for the fabrication of Bi-based lasers. The GaAs0.975Bi0.025 active layer was
grown at 350 °C by molecular beam epitaxy. The lasing oscillation from a GaAs0.975Bi0.025/GaAs semiconductor chip
with a Fabry-Perot cavity was observed by photo-pumping. The characteristic temperature of the laser was 83 K in the
range between 160 and 240 K. The lasing emission peak energy decreased at a constant rate of -0.18 meV/K, which is
40% of the temperature coefficient of the band gap of GaAs in this temperature range. Above 240 K, the lasing threshold
pumping power increased sharply, and the lasing emission peak energy started shifting to higher energies. This result is
probably due to carrier behaviors at the GaAs0.975Bi0.025/GaAs heterointerface, in which a large valence band offset and
an almost flat conduction band offset are expected.
Solid-state dye-doped polymeric distributed-feedback lasers in
near-infrared wavelength
region were fabricated by photo nanoimprint lithography.
Fluorinated-polyimide material
which shows low propagation loss in the near infrared was used as the host matrix of the
active waveguide doped with near-infrared organic dye, LDS950. Single wavelength
lasing emission at 953 nm, which corresponds to the second-order Bragg reflection for the
grating, was observed at room temperature from the laser by
photo-pumping using
nitrogen-gas laser. When the ambient temperature is raised, the lasing wavelength shifts to
shorter at a ratio of 0.094 nm/K between 20 and 50°C, as the effective refractive index of
the active region becomes smaller. The lasing threshold pumping density stays nearly
constant during the temperature variation.
Study on high speed indoor wireless optical LAN system enabling 100Mbps signal transmission with low bit error rate (10-9) is presented. To realize the optical LAN system handling 100 Mbps signal, a directed line of sight (LOS) system is adopted as the optical receiver sensitivity for a bit error rate of 10-9 for 100 Mbps signals is fairly large. In the system, new approaches are introduced: WDM technology which enables bi-directional transmission in full duplex manner is applied using a 1.3 micrometers laser diode for down-link and 0.65 micrometers red laser diode for up-link light sources. As the wavelengths of the two lasers are quite separated from each other, this WDM technology brings an advantage that two kind of semiconductor materials can be used for detectors; GaInAs is used for down-link while Si is applied for up-link. GaInAs PD cannot detect the up-link laser light of 0.65 micrometers and Si PD or APD cannot detect the down-link laser light of 1.3micrometers . Therefore full duplex transmission can be achieved in this configuration. In the indoor wireless optical LAN system, one of the critical points is the transmitter configuration for down- link which enables to deliver optical power enough for 100 Mbps transmission to user areas as wide as possible with inexpensive prices. To realize the point, a special 1.3micrometers laser diode, a spot-size converter integrated laser (SS-LD), is introduced in company with convex lens and an object lens to deliver optical power to areas as wide as possible. As the far-field patterns of the SS-LD are fairly narrow, most of the output power of the LD could be collected to and spread wide by the object lens of 40 magnifications. Using the device, 3m diameter circle area in the plane 2m apart from the 1.3micrometers SS-LD emitting 20 mW optical power, could receive optical power above the receiver sensitivity for a bit error rate of 10-9 for 100 Mbps signals. The visible red light is convenient for not only position setting but also eye-safety problem. Although maximum permissible exposure value at 0.65micrometers is lower than those at longer wavelength, winking response of human eyes for the visible laser light results in higher exposure value. Using 0.65 micrometers visible laser light of 1 mW output power for up- link light source and Si APD for detectors, reasonable area which can receive optical power above the receiver sensitivity for a bit error rate of 10(superscript -9 for 100 Mbps signals was obtained.
(110)-oriented GaInAs(P) quantum well lasers along [001] direction have been fabricated to investigate growth direction effects of the QW structure on laser performance. The structures were grown by two methods; MOVPE and MOMBE. Threshold current densities of the QW lasers were investigated for wide stripes aligned in the [001] and [110] directions from the same wafer. As there is no cleaved facets for lasers along [001] direction, the mirror facets were formed parallel to the (001) face by reactive-ion- etching (RIE) using Bbr3 gas. Strong in-lane anisotropic lasing characteristics in the lasers made of the (110)- oriented QW structures were observed between the [001] and [110]cavity directions. This strong anisotrophy in Jth is believed to come from the stronger oscillator strength in the [001] direction. Fairly low threshold current densities of less than 0.6 KA/cm2 were obtained for the lasers with cavities along [001] direction in spite of the lower reflectivity of the RIE-etched mirror surface. The result in this research shows the expected advantage of the (110) lasers along the [001] cavity direction and suggests an advantage of the (110) QW structure in the application for long wavelength surface emitting lasers.
Inclusion of a small amount of Bi in InAs and GaAs changes the temperature dependent behavior of the band gap. Both InAs1- xBix and GaAs1-xBix tend to have temperature insensitive band gap with increasing Bi content. Raman scattering has been performed on the epilayers of InAs1- xBix and GaAs1-xBix compounds grown by MOVPE technique for varying Bi content. Good single crystalline growth with spatial homogeneity was confirmed using micro- Raman technique. Vibrational modes of InBi and GaBi were observed in the two materials, respectively. In addition, vibrational modes corresponding to Bi and phonon-plasmon coupled modes were also observed. Experimental results indicate that Bi atoms homogeneously replace some of the As atoms in both InAs as well as in GaAs to provide good crystalline structures of InAs1-xBix and GaAs1- xBix compounds, respectively.
A monolithically integrated opto-electronic device is proposed as a fast wavelength-switching light source. This tunable duplex integrated light source comprises two wavelength-tunable distributed Bragg reflector (DBR) laser diodes (LDs), two MQW-electro-absorption optical switches, a Y-shaped waveguide coupler, a MQW-electro-absorption modulator, and two thermal drift compensators (TDCs). The wavelength-switching time of the optical switches was estimated to be 60 ps including a 50-ps rise time for the electrical-pulse generator. The wavelength of a 10-Gbit/s NRZ-modulated optical signal can be switched without bit loss. The function of the TDCs is to keep the device-chip temperature constant. Thermal-transient- induced wavelength drift with a millisecond-order time constant, which has been reported for DBR-LDs, and thermal crosstalk between the tuning regions of the integrated LDs, which causes wavelength fluctuation, are effectively suppressed by thermal-drift-compensation operation using the TDCs.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.