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In this study, we propose a defect structure that enhances the vertical coupling efficiency of circularly polarized light incident on topological waveguides consisting of triangle nanoholes with C6v symmetry arranged in honeycomb lattice. The defect structure was formed by removing triangle nanoholes from a certain hexagonal unit cell around the topological waveguide. As a result of comparing the coupling efficiency with and without the defect structure through three-dimensional finite-difference time-domain analysis, significant improvement in the vertical coupling efficiency was observed over the entire telecom C band (4460%@1530 nm). In addition, it was also found that the wavelength showing maximum coupling efficiency can be controlled over the entire C band by changing the arrangement of the dielectric around the defect structure.

We present a wavelength tunable vertical-cavity surface-emitting laser (VCSEL) constructed by die-bonding a half-cavity InGaAs laser diode (LD) chip onto a silicon-on-insulator chip with a microelectromechanical system electrostatic diaphragm mirror that functions as a Fabry–Perot interferometer. As a result of the short cavity length, the integrated tunable LD has single-mode lasing characteristics with an extremely large coherence length of 150 m or more. The developed wavelength tunable LD is used to perform swept-source optical coherence tomography with a large scan depth, which is applicable to ophthalmic observation for the diagnosis of pathologic nearsightedness based on the measurement of the axial length of an eye.

Heterogeneous material integration technology gives us freedom of material choices in both electronic and photonic devices. In this presentation, status, technology and characteristics of photonic devices in photonic integrated circuits (PICs) on Si (SOI) will be reviewed. Membrane (thin III-V film) PICs can realize low power consumption data transmission on Si substrate. This PICs can be applicable to on-chip interconnection to reduce power dissipation under higher speed transmission. 93 fJ/bit transmission with 20 Gbps has been demonstrated. Hybrid PICs were also demonstrated to realize 10-Tbps-class transceiver with low energy cost for distributed computing. This structure can integrate multiple function and many array devices in one chip. Also, by dense integration, some function of electronics can be moved to photonics part. This enables power consumption reduction.

We propose an Si-based optical vortex beam splitter consisting of topological edge state waveguides with C6 symmetry. The device can continuously change the branching ratio of the propagate light in the range from 16% to 84%.

The energy consumption of light sources must be reduced to realize on-chip optical interconnects. This study proposes a buried-ridge-waveguide (BRW) structure to enhance the lateral optical confinement. An increase in the lateral optical confinement induces the reduction in the threshold current, and it also provides a differential resistance due to a reduction in the distance between the electrode and active region. The stripe width and ridge height are designed considering the internal loss and differential resistance. A comparison between the BRW and conventional flat structures demonstrates a 20% and 35% reduction in the threshold current and differential resistance, respectively.

To advance on-chip optical interconnections, membrane distributed-reflector (DR) lasers with low threshold current and high-efficiency operation at one side output were realized. First, a membrane distributed Bragg reflector (DBR) laser with 80- μ m-long active section and 50- μ m-long DBR section was fabricated to clarify the DBR reflectivity. An external differential quantum efficiency of 35% for the output from the front facet was obtained, and the DBR reflectivity was estimated to be 75%. Next, a membrane DR laser with 61- μ m-long distributed feedback section and 50- μ m-long DBR section was fabricated. A threshold current of 0.48 mA, external differential quantum efficiency from the front side waveguide of 26%, and light output ratio from the front to the rear sides of 13 were obtained. The lasing spectrum showed a single-mode operation with a side-mode suppression-ratio (SMSR) of 40 dB. Finally, small-signal direct modulation was carried out and a modulation current efficiency factor of 7.9 GHz/mA1/2 and 7 GHz/mA1/2 were, respectively, obtained for the 30- μ m-long and 61- μ m-long devices.

On-chip optical interconnection is a promising technology for wiring future large-scale integrated circuits, as a means to mitigate the considerable power dissipation of traditional wiring layers. Here, we fabricate an integrated optical link using a membrane distributed-feedback (DFB) laser and a p-i-n photodiode (PD) in a butt-jointed built-in coupling geometry. The optical link is formed on a Si substrate by benzocyclobutene bonding. The integrated DFB laser shows a low-threshold current of 0.48 mA. Light transmission between the DFB laser and the p-i-n PD is confirmed with static measurements of the optical link. The optical link has a 3-dB bandwidth of 11.3 GHz at a 2.73 mA DFB laser bias current and a –3 V p-i-n PD bias voltage. A data transmission experiment of the optical link is performed, using a nonreturn to zero, pseudorandom-bit-sequence with a word length of 231-1 signals. With a DFB laser bias current of 2.5 mA, 10 Gbit/s data transmission with a bit-error-rate of 6 × 10–7 is successfully achieved.

Record high power conversion efficiency operation of a GaInAsP/InP membrane distributed-reflector laser on silicon substrate was realized. In order to enhance the efficiency, both an improvement of external differential quantum efficiency and a reduction of differential resistance were achieved. As a result, an external differential quantum efficiency from the front facet of 36%, and a maximum power conversion efficiency of 14.6% were obtained for a device with a 40- $\mu \text{m}$ -long active region.

We demonstrate a silicon Mach-Zehnder modulator (MZM) based on hydrogenated amorphous silicon (a-Si:H) strip-loaded waveguides on a silicon on insulator (SOI) platform, which can be fabricated by using a complementary metal-oxide semiconductor (CMOS) compatible process without half etching of the SOI layer. Constructing a vertical p-n junction in a flat etchless SOI layer provides superior controllability and uniformity of carrier profiles. Moreover, the waveguide structure based on a thin a-Si:H strip line can be fabricated easily and precisely. Thanks to a large overlap between the depletion region and optical field in the SOI layer with a vertical p-n junction, the MZM provides 0.80- to 1.86-Vcm modulation efficiency and a 12.1- to 16.9-dBV loss-efficiency product, besides guaranteeing a 3-dB bandwidth of about 17 GHz and 28-Gbps high-speed operation. The αVπL is considerably lower than that of conventional high-speed modulators.

We fabricated a magneto-optical (MO) isolator with a TE mode nonreciprocal phase shift. The isolator is based on a Mach-Zehnder interferometer composed of 3-dB directional couplers, a reciprocal phase shifter, and a nonreciprocal phase shifter. To realize TE mode operation in the optical isolator, we designed a novel waveguide structure composed of a hydrogenated amorphous silicon waveguide with an asymmetric MO garnet lateral clad on a garnet substrate. The isolator operation is successfully demonstrated in a fabricated device showing the different transmittances between forward and backward directions. The maximum isolation of the fabricated isolator is 17.9 dB at a wavelength of 1561 nm for the TE mode.

We proposed a wavelength-grid free WDM system, which allows wavelength drift so that use of uncooled laser and high-density WDM is enabled. A multi-wavelength QD-LD for the system was also demonstrated.

A broadband Si waveguide loop mirror utilizing a curved directional coupler (CDC) was realized for application to an external cavity type III-V/SOI hybrid laser. Reflectance with broad wavelength characteristics was obtained while controlling reflectance value by varying the CDC coupling angle.

We experimentally demonstrate a microring-type magneto-optical (MO) switch with a-Si.H waveguides on a garnet substrate. By controlling the direction of the external current induced magnetic field, an extinction ratio of 9 dB was achieved.

We demonstrated a novel slow-light Si-wire waveguide combined with metamaterials, which can be easily integrated with other Si photonics devices. The slow-light effect can be produced simply by placing metamaterials at an appropriate position on a Si-wire waveguide. It was confirmed that the large group index of more than 40 could be obtained because of a steep and discontinuous change of dispersion relation near the resonance frequency of metamaterials.

As a light source for on-chip optical interconnections, we have been investigating membrane distributed-refiector (DR) lasers with low power consumption operation. This time we would like to present further improvements by adopting a buried-ridge-waveguide (BRW) structure so as to reduce its series resistance, hence energy consumption of the membrane DR laser. We investigated mode distributions of (a) flat type (conventional) buried heterostructure and (b) BRW structure, and calculated the distance between the p-side electrode and the active region, and the differential resistance of them. As the result of theoretical calculation, the differential resistance can be reduced to $180\ \Omega$ for the DFB section length of $30\ \mu\mathrm{m}$ , ridge height $\mathrm{d}=50\ \text{nm}$ and tilted mesa width $\text{Wd} , and this value is around 40% smaller than that of flat type BH structure. To realize such BRW structure, we controlled the growth period of InP by inserting GaInAs marker layers by OMVPE. As a result, the BRW structure with the ridge height $\mathrm{d}=50$ nm and the tilted mesa width $\text{Wd} =0.2\mu \mathrm{m}$ was successfully obtained with the growth time of 4.6 min.

Low-power consumption directly-modulated lasers are a key device for on-chip optical interconnection. We fabricated a GaInAsP/InP membrane DFB laser that exhibited a low-threshold current of 0.21 mA and single-mode operation with a sub-mode suppression ratio of 47 dB at a bias current of 2 mA. A high modulation efficiency of 11 GHz/mAsup1/2/supwas obtained. A 10 Gbit/s direct modulation using a non-return-to-zero 2sup31/sup-1 pseudo-random bit sequence signal was performed with a bias current of 1 mA, which is the lowest bias current ever reported for direct modulation of a DFB laser. A bit-error rate of 10sup-9/supwas successfully achieved.

Replacing part of a conventional optical circuit with a topological photonic system allows for various controls of optical vortices in the optical circuit. As an underlying technology for this, in this study, we have realized a topological converter that provides high coupling efficiency between a normal silicon wire waveguide and a topological edge waveguide. After expanding the waveguide width while maintaining single-mode transmission from the Si wire waveguide, the waveguides are gradually narrowed from both sides by using a structure in which nanoholes with C6 symmetry are arranged in a honeycomb lattice. On the basis of the analysis using the three-dimensional finite-difference time-domain method, we actually fabricated a device in which a Si wire waveguide and a topological edge waveguide were connected via the proposed topological converter and evaluated its transmission characteristics. The resulting coupling efficiency between the Si wire waveguide and the topological edge waveguide through the converter was –4.49 dB/taper, and the coupling efficiency was improved by 5.12 dB/taper compared to the case where the Si wire waveguide and the topological edge waveguide were connected directly.

Transistor Laser (TL) has multiple modulation methods by a combination of terminal connection because it has three electrical terminals unlike the laser diodes. In this report, for the voltage modulation of the TL, the light output response under a large signal voltage modulation was simulated. By considering the transient change of the current in the active layer, we succeeded in reproducing the light output having the peak in the opposite direction to the steady state observed with the actual device so far. Based on the simulation, the optimum collector-base capacitance in the actual device and the minimum required end-facet reflectance for securing a high extinction ratio were obtained.

Membrane distributed reflector (DR) laser exhibited a low threshold current (0.21 mA) and high modulation current efficiency factor of 12 GHz/mA1/2. A 20 Gbit/s direct modulation was obtained with the bias current of 1 mA, which corresponded to the energy cost of 93 fJ/bit.

In order to improve lasing characteristics of 1.3-μm wavelength transistor lasers, device structure was changed by focusing on optical confinement and heat dissipation. As the results, the highest continuous-wave operation temperature up to 90 °C was obtained for the first time.

An energy cost of ridge-waveguide type membrane Distributed-Reflector laser was investigated for 10 Gbit/s and 20 Gbit/s operations. Thanks to its strong optical confinement and reduced resistance, the energy cost could be reduced to approximately 1/2 of that for conventional flat-top-waveguide type membrane DR laser.

Direct modulation lasers are attractive for short-to-mid range fiber communication system. Transistor lasers (TLs), which are hetero-bipolar transistor with an active layer in the base, have a potential to overcome modulation bandwidth limitation of conventional laser diodes (LDs). One of the reasons of the modulation bandwidth limitation of the conventional LDs is delay of carrier diffusion to quantum wells (QWs). With proper design of TLs with some current gain, this delay can be reduced and TLs can have wider modulation bandwidth under the emitter current modulation configuration. In the first part of the presentation, these theoretical analyses will be discussed. By theoretical analysis of TLs with rate equations taking account of carrier diffusion lifetime, 50 GHz modulation bandwidth can be expected with a current gain of ~1.7. Also, by applying voltage bias between the base and collector under the common-base configuration, which causes Frantz-Keldysh effect at the interface layer (GaInAsP in our case), internal loss can be controlled if the bandgap of layers at the interface is appropriately wider than the energy corresponding to the lasing wavelength. This is a kind of “built-in” electro absorption modulator. Therefore, voltage modulation, which corresponds to “loss” modulation, can be configured and has wider modulation bandwidth. The reason why loss modulation has wider modulation bandwidth is that the slope of decay curve of small signal modulation over a relaxation oscillation frequency is slow compared with that of conventional current modulation. In the second part, buried-hetero (BH) regrowth techniques of AlGaInAs QWs will be discussed. AlGaInAs TLs with lasing wavelength of 1.3 µm is very important for fiber communication system. By adopting proper annealing conditions in an organo-metallic vapor-phase-epitaxy (OMVPE) reactor, non-radiative recombination at the AlGaInAs/InP regrowth interface can be significantly reduced even after exposing in the air. Annealing gas, temperature, and the time are important parameters to find optimum annealing conditions. We found using PH3, instead of AsH3, as the annealing gas is effective to remove oxidation at the interface under 650°C, 45-min. annealing. Using this annealing condition, 1.3-µm AlGaInAs BH-LD was realized with a low threshold current density of 140A/cm2/well. Finally, the fabrication process and characteristics of 1.3-µm AlGaInAs TLs will be discussed. Several regrowth steps by MOVPE were required including above mentioned BH regrowth. CW operation up to the temperature of 40°C was demonstrated with both 2 and 3-terminal configurations. For 2-terminal configuration (this means the collector was floating), the threshold current of 33 mA was achieved with the cavity length of 1000 µm and stripe width of 1.7 µm. For 3-terminal configuration, the device shows optical characteristics (I-L) and transistor (collector current) characteristics, simultaneously, under common-emitter and common-base configuration. For the common-emitter configuration, threshold “base” current was reduced by applying voltage between the emitter and collector, On the other side, for the common-base configuration, we observed threshold “emitter” current increase by applying voltage between the base and collector due to Frantz-Keldysh effect. From transistor characteristics, we found Early effect also had an important role for TL characteristics.

We report the first demonstration of direct modulation of InAs/GaAs quantum dot (QD) lasers grown on on-axis (001) Si substrate. A low threading dislocation density GaAs buffer layer enables us to grow a high quality 5-layered QD active region on on-axis Si substrate. The active layer has p-modulation doped GaAs barrier layers with a hole concentration of 5 × 1017 cm−3to suppress gain saturation. Small-signal measurement on a 3 × 580 μm2 Fabry-Perot laser showed a 3dB bandwidth of 6.5 GHz at a bias current of 116 mA. A 12.5 Gbit/s non-return-to-zero signal modulation was achieved by directly probing the chip. Open eyes with an extinction ration of 3.3dB was observed at room temperature. The bit-error-rate (BER) curve showed no error-floor up to BER of 1 × 10−13. 12 km single-mode fiber transmission experiments using the QD laser on Si showed a low power penalty of 1 dB at 5 Gbit/s. These results demonstrate the potential for QD lasers epitaxially grown on Si to be used as a low-cost light source for optical communication systems.

A GalnAs/InP membrane p-i-n photodiode (PD) integrated with a back end DBR was theoretically investigated under a condition of the back reflection of −30dB. As the result, it was found that the 3dB bandwidth of 17 GHz can be obtained with the absorption section length of 12 μm. These are approximately 3 times faster and 1/3 times smaller than those of a similar PD without the back end DBR.

We demonstrate a monolithic integration of lateral-current-injection (LCI)-type membrane-based distributed-feedback (DFB) lasers and p-i-n-photodiodes (PDs) using a butt-jointed built-in (BJB) structure bonded on a Si substrate using benzocyclobutene. The BJB structure to be integrated to the membrane optical devices was prepared by organometallic vapor-phase epitaxy. A threshold current of 280 μA was obtained under a room-temperature continuous-wave condition by adopting a strongly index-coupled DFB laser with a surface grating structure and a λ/4-shift region. A low dark current of 0.8 nA was obtained with the p-i-n-PD at a bias voltage of –1 V, and its photocurrent property coincided with the light output property of the membrane DFB laser.

The direct modulation characteristics of a membrane distributed feedback (DFB) laser on a silicon substrate were investigated. Enhancement of the optical confinement factor in the membrane structure facilitates the fabrication of a strongly index-coupled (κ(I) = 1500 cm(-1)) DFB laser with the cavity length of 80 µm and a threshold current of 270 µA. Small-signal modulation measurements yielded a -3dB bandwidth of 9.5 GHz at 1.03-mA bias current, with modulation efficiency of 9.9 GHz/mA(1/2), which is, to the best of our knowledge, the highest value among those reported for DFB lasers.

Toward the realization of ultralow-power-consumption on-chip optical interconnection, two types of membrane-based GaInAs/InP p-i-n photodiodes were fabricated on Si host substrates by using benzocyclobutene bonding. A responsivity of 0.95 A/W was estimated with a conventional waveguide-type photodiode with an ∼30-μm-long absorption region. The fitting curves based on the experimental data indicated that an absorption efficiency above 90% could be achieved with a length of 10 μm. In addition, increased absorption per length of a photonic crystal waveguide-type photodiode was obtained because of the enhanced lateral optical confinement or the slow-light effect, enabling a further reduction in the device length.

High efficiency operation of membrane distributed-reflector laser was demonstrated by both an improvement in differential quantum efficiency and a reduction of differential resistance. A threshold current of 0.44 mA, an external differential quantum efficiency for the front-side output of 36%, and a maximum power conversion efficiency of 14.6% were obtained for a device with a DFB section length of 40 μm.

Bonding conditions and characteristics of N2-plasma activated bonding for GaInAsP/SOI hybrid lasers are explained. SEM and TEM images reveal high quality bonding interface and less damage quantum wells, which are enough to realize hybrid lasers.

A waveguide optical isolator operating in TE mode was demonstrated with an isolation of 17.9 dB. Amorphous silicon core along lateral walls of magneto-optical garnet was fabricated to induce nonreciprocal phase shift in TE mode.

In this work, GaInAs/InP membrane p-i-n photodiodes integrated with a back-end distributed Bragg reflector were numerically investigated for a backreflection of −30 dB. The results showed that a 3-dB bandwidth of 17 GHz and reverse bias of 1 V can be obtained for an absorption section length of 12 μm. The 3-dB bandwidth is approximately twice faster and the absorption length is 1/3 times smaller compared to those of a similar photodiode without the back-end DBR.

The papers in tihs special section were presented at the IEEE International Semiconductor Laser Conference, which was last held in Palma de Mallorca, Spain, in September 2014 and covered a variety of recent research advances in semiconductor lasers.

10 Gbit/s data transmission through an optical link formed on a Si substrate was carried out by using GaInAsP/InP membrane-based DFB laser and PIN photodiode. The 3dB bandwidth of 11.3 GHz and the BER of 6×10−7 at 10 Gbit/s operation were obtained.

We realized GaInAsP/SOI hybrid Fabry-Perot (FP) laser with AlInAs-oxide current confinement structure for PICs on a silicon platform. Using hybrid wafers by a plasma activated bonding technique, an AlInAs layer just above GaInAsP quantum wells was oxidized by wet oxidation. A threshold current of 50 mA and an external differential quantum efficiency of 11%/facet were obtained with the unoxidezed stripe width of 4.5 µm and the cavity length of 500 µm.

We investigated lasing characteristics of 1.3-µm npn-AlGaInAs/InP transistor lasers under applying the collector-base voltage V CB with common base configuration. By simultaneous measurement of laser and transistor characteristics, it was revealed that the Early effect of transistors was main reason of threshold current degradation and output power reduction. We also observed that the red-shift of the peak lasing wavelength depends on collector-base voltage VCB and these behaviors may be explained by the quantum-confinement Stark effect (QCSE).

We report a waveguide optical-to-THz (200 GHz to 300 GHz) signal converter using ring-shaped microstripline with GaInAs photoconductive mesa structure. A maximum extinction ratio of 16.8dB in THz band was obtained with light irradiation of 15dBm.

Recent advances of GaInAsP/InP membrane lasers will be presented. A high index-coupling grating structure enabled very-low threshold current (230 μA) as well as high-speed modulation with a record modulation current efficiency (9.9 GHz/mA1/2).

The influence of in-situ thermal cleaning on the regrowth interface quality of 1.3-μm wavelength AlGaInAs/InP-buried-heterostructure (BH) lasers grown by organo-metallic vapor-phase epitaxy was investigated. The surface recombination velocity estimated from below threshold electroluminescence measurements was used to quantitatively study regrowth interface quality. The relationship between surface recombination velocity and lasing properties was supported by theory. In this way, we could validate the use of surface recombination velocity as a measure of interface quality. In-situ thermal cleaning at 650°C for 45 min under PH3 atmosphere resulted in operational BH lasers (1.6 μm stripe width) with a differential quantum efficiency of 66% and an internal quantum efficiency of approximately 76%.

High-speed direct modulation capability was investigated in 1.55-μm GaInAsP/InP distributed reflector (DR) lasers with wirelike active regions in terms of carrier transport from GaInAsP optical confinement layers (OCLs) to the active regions. Theoretical analysis revealed strong dependence of the modulation bandwidth on the thickness of the OCLs and width of the wirelike active regions. To confirm this prediction, two DR lasers with OCLs of different thicknesses (120 and 40 nm) were fabricated and their 3-dB bandwidths (f3 dB) under small-signal modulation were compared. The device with the narrower OCL exhibited f3 dB exceeding 15 GHz and clear eye opening under 25 Gb/s modulation, whereas that with the thicker OCL had f3 dB of only 2 GHz. These results were in good agreement with the theoretical predictions.

Photonic integrated circuits (PICs) produced by large-scale integration (LSI) on Si platforms have been intensively researched. Since thermal diffusion from the LSI logic layer is a serious obstacle to realizing a Si-based optical integrated circuit, we have proposed and realized athermal wavelength filters using Si slot waveguides embedded with benzocyclobutene (BCB). First, the athermal conditions were theoretically investigated by controlling the waveguide and gap width of the slot waveguides. In order to introduce the calculated waveguide structures to wavelength filters, the propagation losses and bending losses of the Si slot waveguides were evaluated. The propagation losses were measured to be 5.6 and 5.3dB/cm for slot waveguide widths of 500 and 700nm, respectively. Finally, athermal wavelength filters, a ring resonator, and a Mach-Zhender interferometer (MZI) with a slot waveguide width of 700nm were designed and fabricated. Further, a temperature coefficient of -0.9pm/K for the operating wavelength was achieved with the athermal MZI.

Small- and large-signal analyses of transistor lasers (TLs) are demonstrated for 0.98-μm wavelength GaInAs/GaAs and 1.3-μm AlGaInAs/InP systems. The modulation bandwidth of the TL was larger than that of a laser diode due to the lower damping effect in the former. Comparisons between TLs with different numbers of quantum wells indicated that a large signal response and high modulation bandwidth could be realized simultaneously. However, in the case of large-signal analysis, the calculated eye diagrams were degraded by a resonance oscillation peak. By changing structural parameters such as the facet reflectivity and by controlling the damping effect, the resonance frequency peak was suppressed and clear eye diagrams of >;40 Gb/s were obtained.

We demonstrate 10 Gbit/s operation of InAs/InGaAs quantum dot (QD) p-i-n photodiodes (PDs) grown on on-axis (001) GaP/Si substrates. A 3.0 × 50 μm2 QD PD shows a small dark current of 0.2 nA at a bias voltage of −3 V, which corresponds to a dark current density of 0.13 mA/cm2. This low-dark current characteristic obtained from a narrow-stripe device indicates that sidewall and threading dislocations have small effects on the dark current. The 3 dB bandwidth was 5.5 GHz at a bias voltage of −5 V. Large signal measurement with non-return-to-zero signals shows 10 Gbit/s eye opening.

Heating rate dependence of glass transition and crystallization temperatures is applicable for evaluation of glass structural stability and also for discussion on the apparent activation energies for glass transition and crystallization. The glass-structure stabilities of the Zr-based BMGs (Zr50Cu40Al10, Zr70Cu20Al10 and Zr70Ni20Al10) and the conventional amorphous alloys (Zr70Cu30 and Zr70Ni30) are assessed by the densely packed glass structure as well as the complicated crystallization process. By the reverse Monte Carlo (RMC) simulation with X-ray and neutron diffraction data, it is shown that the densely packed structure is built by icosahedron-like clusters. In Zr65Al7.5Ni10Pd17.5 and Zr65Al7.5Ni10Cu17.5, the effect of Pd atoms on the glass structure is also described.

金沢大学理工研究域電子情報学系, A room-temperature pulsed operation was demonstrated using lateral current injection-type lasers composed of a 400-nm-thick GaInAsP core layer with compressively strained 5 quantum wells. A threshold current of 105 mA and corresponding density of 1.3 kA/cm2 (260 A/cm2 per well) were obtained with the stripe width of 5.4 μm and the cavity length of 1.47 mm. A fundamental transverse mode operation was obtained with the narrower stripe device of 2.0 μm and the cavity length of 805 μm, while the threshold current and corresponding density were 49 mA and 3.0 kA/cm 2, respectively. © 2009 Optical Society of America.

Wavelength modulation over 500 kHz by a micromechanically tunable vertical-cavity surface-emitting laser (VCSEL) consisting of an InP-based half-VCSEL chip and a micromachined silicon-on-insulator chip with a concave movable mirror has been demonstrated for the first time. A peak power of 3.5 mW, a tuning range of 55 nm, and a side-mode suppression ratio of about 60 dB have been demonstrated.

Sub-mA threshold current operation (as low as 0.8 mA) of distributed reflector (DR) lasers with wirelike active DFB section and passive DBR section was realized at room temperature continuous wave condition utilizing narrow laser stripe (2.1 mum) and strong index coupling coefficient of 450 cm-1.

We realized strongly index-coupled membrane buried-heterostructure (BH) distributed-feedback (DFB) lasers fabricated by electron-beam lithography, CH4/H2 reactive-ion etching, and regrowth by organometallic vapor-phase epitaxy, using surface corrugation DFB. First, we fabricated narrow stripe membrane BH-DFB lasers with surface corrugation for stable single-mode operation. Under optically pumped room-temperature continuous-wave (RT-CW) operation, a wide stopband width of 68 nm was observed in spite of the narrow stripe width of 0.6 mum. The corresponding index-coupling coefficient of 2950 cm-1 is over two times larger than that of a flat-surface (conventional) membrane BH-DFB laser with a stripe width of 2.0 mum. In addition, we fabricated a short-cavity membrane DFB laser with a surface corrugation structure. A threshold optical pump power of as low as 0.34 mW was realized for a 2.0-mum-wide and 80-mum-long device under RT-CW conditions.