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In this paper, we present a liquid-droplet-heating system using a surface acoustic wave (SAW) device. When liquid is placed on a Rayleigh-SAW-propagating surface, a longitudinal wave is radiated into the liquid. If the SAW amplitude increases, the liquid shows non-linear dynamics, such as vibrating, streaming, small droplet flying, and atomizing. This phenomenon is well known as SAW streaming. The liquid temperature is measured during the longitudinal wave radiation and found to increase. First, the mechanism of the liquid-heating effect is discussed on the basis of experimental results. The surface electrical condition is changed to investigate the effect of dielectric heating. The obtained results indicate that the radiated longitudinal wave causes liquid heating and the dielectric heating effect does not. Second, the fundamental properties of the liquid temperature are measured by varying the applied voltage, duty factor, and liquid viscosity. The liquid temperature is found to be proportional to the duty factor and the square of the applied voltage. Therefore, the liquid temperature can be controlled by these applied signals. Also, by using highly viscous solutions, the liquid temperature is increased to more than 100 °C. Moreover, for chemical applications, the possibility of periodic temperature control is tested by varying the duty factor. The obtained results strongly suggest that an efficient thermal cycler is realized. A novel application of the SAW device is proposed on the basis of SAW streaming.

For a multimode-optical-fiber surface plasmon resonance (SPR) sensor with a gold film supporting surface plasmon waves (SPWs), we have investigated the effects of gold thickness on sensor performance experimentally to find the optimal thickness when a white-light source is used. It is found that the sensor with a thickness of around 65 nm enables most precise measurement of a resonance wavelength and gives relatively high sensitivity, which is 1557 nm/RIU in the refractive index range of 1.333–1.3469. Also, we have confirmed that a simulation model based on meridional rays cannot explain the minimum reflectance of SPR spectra for values below 0.5.

A way to improve the angular sensitivity of surface plasmon resonance (SPR) biosensor by tuning the resonance position to a higher incident angle region using a lower refractive index glass prism is described in this paper. A novel effective 3-layer (E3L) model is described to transform a multiple layer biosensor configuration in context of SPR condition. The E3L model supports the use of a low refractive index prism for biosensing. The performance of the sensor in immunosensing is checked for two glass prisms of different refractive index materials. The experimental results showed an enhancement in the amount of resonance angle shift of the immunosensor for the lower refractive index glass prism.

When a Rayleigh surface acoustic wave (SAW) propagates at a liquid/solid interface, it radiates its energy into the adjacent liquid. If a liquid droplet is loaded on the SAW propagation surface, droplet vibration, streaming, jetting, and atomization are observed. These phenomena are called SAW streaming. In this paper, a novel thin-film deposition method based on the atomization of SAW streaming phenomena is proposed. The liquid with film material is loaded on the SAW propagation surface and the liquid is atomized. The atomization direction depends on the Rayleigh angle, which is determined by the sound velocity in the liquid and the SAW velocity. For easy fabrication of a thin uniform film, the atomization direction is controlled in the perpendicular direction. Using the developed system, the deposition of pigments in ink is carried out. The results observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) indicate that a pigment layer is formed on a glass plate.

A longitudinal wave is radiated into a liquid when the liquid is placed on a surface acoustic wave (SAW) propagating surface. The radiated longitudinal wave induces liquid dynamics, such as vibrating and streaming. This phenomenon is called SAW streaming. The liquid's temperature increases, as the radiated longitudinal wave becomes attenuated inside the liquid. In this paper, the measurement and observation results of temperature and streaming in liquids are described. First, the sol–gel formation of agar–agar is observed. Second, a highly viscous liquid droplet is placed on the SAW propagation surface. However, the stable measurements are difficult. Therefore, a U-type cell is developed and the pattern of the streaming in this cell is observed. The results show that there is an association between the attenuation of a longitudinal wave and the temperature distribution.

In this paper, we present the fundamental characteristics of a novel dual-colour optical fibre surface plasmon resonance (SPR) sensor for a portable low-cost sensing system. The principle of the proposed SPR sensor is based on the differential reflectance method. Light from two light-emitting diodes (LEDs), which are flashing alternately with different wavelengths, is fed to a sensor via two optical couplers. The reflected light is detected by a photodiode. Changes of reflectance at two wavelengths are proportional to the refractive index change of the medium of interest. Taking the difference in reflectance at two wavelengths improves the sensitivity almost twofold. Measuring ethanol solutions with different refractive indices reveals that the sensor has a linear response to the refractive index change from 1.333 to 1.3616. By measuring the stability in the time response we estimate that the limit of detection (LOD) of the refractive index is 5.2 × 10−4.

The authors examine the reflectivity of the quasi-graded distributed Bragg reflector using the stopband width. The stopband width of about 1000 AA for a reflectivity of about 99% is able to be measured with an accuracy of +or- 1 AA. Thus, the reflectivity is determined with high accuracy from the stopband width. It is found that the quasi-graded distributed Bragg reflector is a high-quality reflector with high reflectivity and low resistance. >

Electronic-optical conversion efficiency of 11.4% in a vertical-to-surface-transmission electrophotonic device with a vertical cavity is reported. Reduction of the electrical resistance by the double mesa structure, efficient confinement of carriers in the active region by the proton implanted structure, and photon recycling by sidewall reflectors lead to this high conversion efficiency. Efficiency over 10% is achieved for the first time in surface-emitting devices. >

We realized extremely high absolute thickness controllability around ±0.3% in molecular beam epitaxy growth of distributed Bragg reflectors, using a modified reflection high energy electron diffraction oscillation measurement technique. Very low threshold current density and high efficiency were obtained in InGaAs/AlGaAs surface emitting lasers by using this technique and a new periodically doped distributed Bragg reflectors.

The vertical to surface transmission electrophotonic device has a laser cavity covered with plated gold, which has high reflectivity. The laser light is emitted from the distributed Bragg reflector (DBR) with no gold. Consequently, spontaneous emission remains in the laser cavity, and the carriers are regenerated. The injected carriers are converted to light and spontaneous emission is reconverted to carriers. Due to photon recycling, threshold current density decreases and indistinct threshold laser operation is obtained. In the indistinct threshold operation, the light output is linearly polarized. The submode suppression ratio is larger than 25 dB, and the divergence angle of a far field is as narrow as 6.8 degrees . The indistinct threshold laser characteristics lead to high slope efficiency in low current level. To achieve high slope efficiency in the overall current level, DBR mirrors are designed, and high slope efficiency of 0.32 mW/mA is obtained. >

Surface emitting optical devices with a vertical cavity have been investigated for applications in optical interconnections. To integrate these devices into a two‐dimensional array, it is necessary to improve the conversion efficiency from electrical power to optical power. To meet this requirement, the series resistance of the distributed Bragg reflectors that form the vertical cavity must be reduced. This article demonstrates the reduction in the series resistance of the distributed Bragg reflector by introducing quasi‐graded superlattices at the heterointerfaces. By using this structure, we obtain a low series resistance distributed Bragg reflector without compromising the high reflectivity. The mechanism of the reduction in the series resistance is studied and it is found that an increase in tunneling current leads to a decrease in the resistance. The dependence of tunneling current on doping concentration of the distributed Bragg reflector and the superlattice structure is also discussed.

Surface emitting laser operation and optical switching operation are demonstrated in vertical-to-surface transmission electrophotonic devices using pnpn structures and vertical cavities. Threshold current density as low as 1.4 kA cm−2 for laser operation and optical switching energy as low as 2.2 pJ for optical switching operation are achieved. It is found that optical switching energy can be lowered by multireflections in the vertical cavity. Growth rate calibration and series resistance in the distributed Bragg reflector mirrors are examined for device fabrication.

In optical interconnection, the cascade optical interconnection using two-dimensional optical switch devices is an important basic structure. To realize such an optical interconnection, the vertical-to-surface transmission electrophotonic device (VSTEP), which has a planar structure easy for two-dimensional integration and is capable of light emission, light detection, and latching, has been developed. Utilizing the optimized combination of a pnpn thyristor structure, double heterojunction structure and vertical cavity structure, efficient laser mode emission and switching characteristics were obtained. In the optical interconnection using the differential structure, optical switching was achieved with optical energy as low as 150 fJ. An operating speed of 25 MHz was confirmed in the continuous mode. In addition, using the cascade characteristic in the device-to-device interconnection, the shift-register operation was carried out using the optical interconnection between four optical array switches.

With the continuing development of biotechnology and nanotechnology, a miniaturized and integrated device that is capable of controlling and measuring a small droplet has become desirable. Using a surface acoustic wave (SAW), a droplet is manipulated. If the sensor is fabricated onto the SAW propagating surface, a novel sensor and actuator integrated system, namely digital microfluidic system, is realized. The integrated device is called a “micro-laboratory.” In this paper, to actualize a disposable micro-laboratory, three-layer structure of sensor plate/ matching layer/ piezoelectric substrate is examined. Droplet manipulation, mixing and measurement are succeeded using the proposed novel micro-laboratory.

In this paper we present practical capability of a dual-color optical fiber surface plasmon resonance (SPR) sensing system for measuring the refractive index (RI) of liquids. The sensor system consists of two LEDs, two optical couplers, a photodiode and an electronics followed by a laptop computer via an A/D converter. Features of the developed system are compact, portable and inexpensive. Principle of the proposed SPR sensing system is based on the differential reflectance method. Changes of reflectance at two wavelengths are proportional to the refractive index change of a sensed medium. Differential of two reflectance gives two-folded sensitivity. Three liquids with different RI ranges were tested. Also the reproducibility of measured data was checked. As a result, it was demonstrated experimentally that the dual-color optical fiber SPR sensing system is capable of measuring the RI of liquids over the range of from 1.329 to 1.36 with the RI resolution of 2.35 × 10-4.

In this paper, we present a liquid-droplet-heating system using a surface acoustic wave (SAW) device. When liquid is placed on a Rayleigh-SAW-propagating surface, a longitudinal wave is radiated into the liquid. If the SAW amplitude increases, the liquid shows nonlinear dynamics, such as vibrating, streaming, small droplet flying, and atomizing. This phenomenon is well known as SAW streaming. The liquid temperature is measured during the longitudinal wave radiation and found to increase. The fundamental properties of the liquid temperature are measured by varying the applied voltage, duty factor, and liquid viscosity. The liquid temperature is found to be proportional to the duty factor and the square of the applied voltage. Therefore, the liquid temperature can be controlled by these applied signals. Also, by using highly viscous solutions, the liquid temperature is increased to more than 100 C. Moreover, the possibility of periodic temperature control is tested by varying the duty factor. The obtained results strongly suggest that an efficient thermal cycler is realized. A novel application of the SAW device is proposed on the basis of SAW streaming

The authors experimentally study the effect of a sidewall reflector on current versus light-output characteristics in a pnpn vertical-to-surface-transmission electrophotonic device with a vertical cavity. The distributed Bragg reflectors that form the vertical cavity for laser oscillation and the sidewall reflector retain spontaneously emitted photons in the optical cavity, and only the photons that have the resonance wavelength of the vertical cavity are emitted. As a result, spontaneously emitted photons are absorbed and the carriers are regenerated; that is, the injected carriers are converted to light, and spontaneous emission is reconverted to carriers. As a result of photon recycling of spontaneous emission, threshold reduction is expected. Threshold reduction by at least a factor of 4 is obtained with a device that has the sidewall reflector. >

Surface-Emitting-Laser-based optical functional devices have promising features for photonic switching and optical data processing. All photonic switching networks need control signals to be sent into the nodes to allow for appropriate routing of traffic.') Control injection, thus, must be taken into consideration more in photonic switches. An optical self-routing switch has been proposed where a node consists of pnpn-Vertical to Surface Transmission ElectroPhotonic Devices with Vertical Cavities (VC-VSTEPS).~) The routing for optical data signals are controlled by an optical pilot signal placed at the head of the optical data signals. However, this switch still needs electric timing signals to be applied to the VC-VSTEPs, which might cause electromagnetic interferences among a large number of internal electric lines, and a delay in the timing signals due to parasitic capacitances. Therefore, it is desirable that the timing signals are further injected optically. This paper reports on VSTEP-based pixels aiming for optically controllable nodes. The pixel consists of a VSTEP using a four-terminal pnpn structure with two distributed Bragg reflectors (DBRs) (Fig. 1). The fabrication process includes two-step mesa etching: 1) to the n-doped gate layer, and 2) to the n-doped DBR layer. The n- and p-gate electrodes are formed on the second mesa with Zn diffusion for the p-gate. In comparison to twoterminal VC-VSTEPs3), the structure provides variable switching voltage characteristics and gate turn-off operation by means of carrier injectiodextraction through the gate terminals. Also, this structure allows the formation of a hetero-junction bipolar transistor (HBT), or a hetero-junction photo-transistor (HPT) together with the pnpn-structure. These two features, in combination, expand flexibility in device configuration to meet the demands of photonic switching and processing systems. As an example, a pixel has been demonstrated for an optical self-routing switch with optical gating and optical reset operations. Figure 2 shows an equivalent circuit of the pixel. When the optical gate pulse is incident on the HFT1, current is injected to the pnpn device, resulting in a reduction of switching voltage, and allowing turn-on by the input optical pulse. Applying the gate pulses to the pixels with proper time delays, the pilot signal can select one pixel in which the pilot signal coincides with the gate signal. "2 is used for the optical reset. The optical reset pulse incident on the HPT2 removes the stored charge in the pnpn-device through the ngate. Figure 3 shows voltage-current and light-current characteristics of the fabricated device with various current injections from the n-gate. The switching voltage without n-gate injection is 3.8 V and the threshold current is 35 mA. A common-emitter current gain of 180 is obtained for the npn-HPT using an n-gate as a collector and a cathode as an emitter. Figure 4(a) shows the optical gating operation. A bias voltage of 3V was applied to the anode. The reset is also achieved as shown in Fig. 4(b). Optical energies obtained for the input, gate and reset are 8.0 pJ, 0.5 pJ and 10 pJ, respectively. Reduction in these values will be achieved by a decrease in device size.

The dependence of threshold current density on indium composition in strained InGaAs/AlGaAs quantum well lasers is examined. A threshold current density (J th) as low as 115 A/cm2 is obtained in a chip with a 500 µm long cavity at a lasing wavelength of 950 nm. The J th for a strained InGaAs QW was found to be 35% less than that for a GaAs QW laser with the same cavity length. Time resolved photoluminescence measurement revealed that the improvement in the nonradiative carrier lifetime for quantum wells with higher indium composition was limited to a J th improvement of only 10%. Calculation suggests that the most likely reason for the major portion of the J th improvement is gain enhancement due to a reduction in heavy hole mass.

Vertical-to-surface transmission electrophotonic devices with a vertical-cavity are described. The individually accessed 12/spl times/4 arrays are characterized and demonstrated to have uniform room-temperature continuous-wave operating characteristics for a threshold current of /spl sim/2.8/spl plusmn/0.15 mA and a slope efficiency of /spl sim/0.18/spl plusmn/0.012 W/A with a single transverse mode. Both low threshold and high efficiency with 5% and 7% deviation, respectively, are achieved simultaneously. These devices can be used to constructing two-dimensional massively parallel optical interconnections. >

Bidirectionally cascadable optical pixels that consist of a single-vertical-cavity surface-emitting laser (VCSEL) thyristor and a double-vertical-cavity phototransistor are proposed. Despite almost identical layer structures, each device characteristic can be independently optimized by introducing a lambda /2-spacer layer into the phototransistor section. A lasing threshold of 0.8 mA and a slope efficiency of 0.25 W/A are obtained for the laser thyristor, and a flat-topped photocurrent spectrum over 30 A and a photocurrent gain of 70 A/W are obtained for the phototransistor at the resonant wavelength. This work demonstrates the possibility of monolithic integration using thermal desorption and a regrowth technique and the suitability of these devices for massively parallel optical interconnections. >

A new in situ fabrication process for GaAs is developed. In this process, electron‐ cyclotron‐resonance oxygen plasma is used for the first time to form an oxide mask for Cl2 gas etching. Using this technique, the time and oxygen gas pressure required for the oxidation are drastically reduced, compared to other oxidation methods. Line patterns with submicron width are successfully fabricated by partial modification of the oxide mask by electron beam irradiation and subsequent Cl2 gas etching.

We examine the optical switching characteristics in vertical cavity surface‐emitting laser‐type vertical‐to‐surface transmission electrophotonic devices (VC‐VSTEPs) with a pnpn structure. It is theoretically and experimentally demonstrated that both optical input/output characteristics are strongly influenced by the structure of the vertical cavity. With improvements in optical power output due to laser oscillation, optical switching speed is enhanced by two orders of magnitude compared to spontaneous emission‐type VSTEPs. A 20‐μm‐square VSTEP with an optimized vertical cavity structure demonstrates a low optical switching energy of 2.2 pJ with a switching time of 10 ns, as low as spontaneous emission‐type VSTEPs.

Sidewall recombination in SiO2‐capped GaAs/AlGaAs multiple quantum well mesa structures is investigated using a time‐resolved photoluminescence technique. Nonradiative recombination lifetimes in annealed samples are improved significantly compared with those in samples which are not annealed. This effect contributes to a reduction in sidewall recombination velocity due to disordering of quantum wells at the sidewall by cap annealing. Numerical analysis is used to fit the experimentally observed sample size dependence of the nonradiative lifetimes to calculated curves. This shows that the effective sidewall recombination velocity is reduced from 8×106 to 4×104 cm/s.

We demonstrate the first surface‐emitting laser operation in a vertical‐to‐surface transmission electrophotonic device with a vertical cavity. The thyristor‐like current‐voltage characteristics, which are required for optical and electrical switching, are achieved. Threshold current during the on state is as low as 1.2 mA. All 100 devices, which were randomly extracted from a grown wafer, emit laser light.

A dynamic reconfiguration of optical interconnections for enhanced flexibility in photonic switching systems is realized using a two‐dimensional vertical to surface transmission electrophotonic (VSTEP) device array. A matrix operational scheme for the VSTEP array is proposed and demonstrated. Through this operation, functions for light emission and for electrically programmable spatial light modulation are obtained in a single chip of the VSTEP array and a high‐speed electronic addressing of 1 ns per one line for the matrix is also confirmed.

Bi-directionally cascadable optical pixels comprising low-threshold (1mA) high-efficiency (0.25W/A) surface-emitting laser-thyristors and wide-bandwidth (50Å) high-photocurrent-gain (230A/W) double vertical-cavity phototransistors are described.

We have proposed a structure for optical pixels consisting of a double vertical-cavity detector and single vertical-cavity laser section. This pixel can be formed by simple fabrication processes because the structures of the detector and laser section are almost the same, and the characteristics of the laser and detector sections can be independently optimized by choosing the pair number of each distributed Bragg reflector. We have achieved a spectral bandwidth and peak absorptivity of the double vertical-cavity detector section about five times those of the single vertical-cavity laser section.

With the continuing development of biotechnology and nanotechnology, a miniaturized and integrated device that is capable of controlling and measuring a small droplet has become desirable. Therefore, we fabricated an integrated device by adopting surface acoustic wave (SAW) streaming to control a droplet and an interdigitated electrode (IDE) sensor to measure the impedance of the droplet. The integrated device is called a "micro-laboratory". In this work, a micro-laboratory was realized by fabricating an interdigital transducer (IDT) for generating SAWs and an IDE for measuring a droplet on a single piezoelectric crystal. In the experiment, water and glycerol were mixed by SAWs and water/glycerol mixtures were measured by the IDE sensor. From the result, we found that the mixtures were uniformly mixed by the SAWs. Moreover, as a new application, we fabricated a novel micro-laboratory using an isotropic material/matching layer/128YX-LiNbO3 structure (three-layer structure). By using the three-layer structure, a disposable and low-cost SAW device was realized.

A shear horizontal surface acoustic wave (SH-SAW) sensor can be used to detect the properties of liquids. We propose one application of the SH-SAW sensor as a viscosity sensor. The Japanese Industrial Standards Committee (JISC) has determined the standard liquids used to calibrate a viscometer. If the SH-SAW sensor is to be commercialized, it is necessary that the viscosities of these liquid can be measured. In this study, the standard-viscosity liquids are measured using the SH-SAW sensor operating at different frequencies. The sensor responses to the standard-viscosity liquids are less than those for a glycerol/water mixture. This is due to the viscoelasticity of the standard-viscosity liquids. A simple viscoelastic model is applied to explain the experimental results.

Characteristic uniformities in a vertical to surface transmission electro-photonic device matrix are studied using a double heterostructure optoelectronic switch as an element device. Uniformity of switching voltage and optical switching energy, which is critical in optical parallel operations, is shown over an entire matrix including 64 monolithically integrated elements.

We used two‐step molecular beam epitaxial (MBE) growth to integrate monolithically single and double vertical‐cavity structures on a wafer. This technique is useful for making a single vertical‐cavity surface‐emitting laser–thyristor with a low threshold and a double vertical‐cavity heterojunction phototransistor with both a high responsivity and a large spectral bandwidth. Regrowth on a patterned distributed Bragg reflector after thermal desorption of a passivating GaAs layer resulted in the laser in the single‐cavity section having a threshold current density of 1.0 kA/cm2, which is comparable to that of one grown by conventional one‐step MBE. Controlling thickness to within ±0.3% resulted in the regrown double‐cavity section having a bandwidth of 5 nm.

We demonstrate a record low threshold current of 190 µA in a microcavity surface-emitting laser with a 5-µm-diameter airpost, in pulsed operation at room temperature with no heat sink. This low threshold current is attributed to high-quality epitaxial layers and a dry-etched smooth sidewall.

GaAs wires completely embedded in AlAs are successfully grown by molecular beam epitaxy at substrate temperatures higher than 725°C without interrupting growth. Crescent-shaped 1800-Å-wide GaAs wires are embedded in AlAs using this technique and electron beam lithography. We also investigate the dependence of photoluminescence on the GaAs wire width at room temperature. This investigation indicates that the emission efficiency of the narrowest GaAs wires (1800 Å wide) is at least as high as that of a quantum well grown on a planar substrate.

Very smooth and vertical etching of InP by Cl2 reactive ion beam etching has been achieved under high temperature (≈200°C), high ion energy (≈1 keV) and low Cl2 pressure (∼10-5 Torr). The roughness is estimated to be a few nm by scanning tunneling microscopy and no contamination except for Cl was observed by in situ Auger electron spectroscopy. Under these etching conditions, the etched depth is precisely controlled (σ=22 nm) by simply monitoring the electrode curtent of the ion accelerating grid. Other III-V compound semiconductors, such as GaAs, InGaAs, AlGaInP and InAlAs have also been etched smoothly and vertically. Multilayers of these materials, such as InP/InGaAsP, AlGaInP/GaInP, and InAlAs/InGaAs/InP have been etched without steps between the layers on the sidewalls.

A new electron beam (EB) patterning process capable of resistless nanofabrication for GaAs has been developed using enclosed continuous‐vacuum processes. These processes are surface oxidation by electron cyclotron resonance (ECR) O2 plasma, oxidized‐surface modification by EB irradiation, and subsequent etching by Cl2 gas. The time and oxygen gas pressure required for the oxidation are greatly reduced, compared to other oxidation methods, by using ECR plasma to form an oxide mask for Cl2 gas etching. The plasma‐oxidized mask without EB irradiation cannot be removed by Cl2 gas etching even for 4 h at a sample temperature of 100 °C. In spite of its resistance to Cl2 gas etching, the mask can be easily removed by thermal treatment of the sample at about 620 °C in an As atmosphere.

Smooth and vertical InP reactive ion beam etching has been achieved with electron cyclotron resonance Cl2 plasma at high ion energy (≥900 eV), high temperature (230°C) and relatively low Cl2 pressure (∼10-4 Torr). Smooth etching of an InP system by Cl2 plasma has often been reported as difficult compared to that of the GaAs system due to low volatility of reactive products such as InCl x . In the present work, precise control of incident ion energy and Cl2 pressure contributed to the improvement of both the vertical profile and bottom smooth surface under high substrate temperature (∼200°C). Vertical profiles were easily achieved even at high temperatures by varying the Cl2 pressure. While etching conditions suitable for vertical wall-formation were maintained, surface morphology was drastically improved by increasing ion energy above 900 eV and the bottom roughness became less than 100 nm at 1450 eV.

Monolithically integrated 8×8 semiconductor optical matrix switches have been successfully fabricated for the first time. They were constructed on GaAs substrates from 64 GaAs/AlGaAs electro-optic directional couplers using a simplified tree architecture. The devices have a chip size of 26.5×3 mm2 and a minimum total loss (excluding coupling loss) of 8.7 dB.

The threshold current dispersion, slope efficiency and lasing wavelength of vertical-to-surface transmission electrophotonic devices with vertical cavities are investigated. The critical number of output distributed Bragg reflectors (DBRs) required to overcome the disturbance due to back-surface reflections for surface-emitting-laser (SEL) structure devices is clarified. >

We demonstrate surface-emitting laser operation in pnpn structure vertical to surface transmission electro-photonic devices (VSTEPs) with a vertical cavity, i.e., VC-VSTEPs. Continuous-wave (cw) laser operation at room temperature is achieved with a VC-VSTEP mounted directly on a glass sheet with no heat sink. The threshold current is 3 mA for a 10 µm square device. In pulsed operation, this device shows current vs light-output characteristics with no definite threshold. The light output spectrum shows single mode operation in which the spectral width is the same value as the resolution of a spectrometer.