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A detailed study to achieve optically efficient GaInNAs QWs by low-pressure metal-organic chemical vapor deposition (LP-MOCVD) is reported. It was found that the insertion of GaNAs/InGaAs layers to GaInNAs QW/GaAs barrier is very effective to control the emission wavelength and improve the optical property of QW. Indium rich (as high as 40%) GaInNAs QWs grown at higher V/III ratio are more desirable to extend emission wavelength over 1.3 μm due to reduced incorporation of impurities. The optical efficiencies of the QW structure were confirmed by the lasing performance in edge-emitting laser. The threshold current density and slope efficiency per facet of a 1360 nm laser diode are measured to be 892 A/cm2 and 0.135 W/A, respectively.

A comprehensive study to achieve optically efficient GaInNAs quantum wells (QWs) grown by low-pressure metalorganic vapor phase epitaxy (MOVPE) has been accomplished. In order to extend emission wavelength over 1.3 μm effectively, GaInNAs QW structures with multiple barriers of GaNAs/InGaAs were proposed. Significant improvement of photoluminescence efficiencies and easy controllability of emission wavelengths over the 1.3 μm range were demonstrated with the proposed structure. It is believed that the wavelengths emitted from our employed QW structures are correlated to the amount of strain, determined by the strain competition between InGaAs (compressive) and GaNAs (tensile) layers. As N contents increased in the QWs, the emission wavelength was able to extend up to 1.38 μm without deteriorating spectral width.

We report an improved optical pumping efficiency in a vertical-external-cavity surface-emitting laser (VECSEL) by employing the double-band mirror (DBM), which acts as a pump beam reflector as well as a cavity mirror. The optical pumping efficiency of a VECSEL with the DBM was increased by 23%, as compared to one with the conventional distributed Bragg reflector. It was found that the use of the DBM was more effective in the VECSEL with the shorter absorption layer thickness.

We report a high-power fundamental transverse mode operation of an optically pumped 920-nm vertical-external- cavity surface-emitting laser. The effects of the gain related structural parameters on the laser performance are investigated. Based on the optimization of the gain structure and the thermal management, a maximum pump-limited output power of 12 W in a TEM00 mode with a slope efficiency of 58% (input power of 24 W) was achieved at room temperature.

We propose a novel lens-less optical end-pumping scheme and report on the development of a highly efficient and compact green vertical-external-cavity surface-emitting laser (VECSEL). A constant-wave pump-power-limited maximum green output power of 1.1 W and an optical-to-optical conversion efficiency of as high as ~15.7% (=1.1 W/7 W) were achieved using a single chip pump laser diode placed directly behind the VECSEL structure without any beam focusing and shaping optical elements.

We characterize the lasing properties of two configurations of end-pumped vertical-external-cavity surface-emitting lasers: one with an intracavity diamond heat spreader, the other with an extracavity heat spreader. A pump-power-limited CW output power of 9.2 W at 1060 nm and a slope efficiency of ~50.3% are achieved with the extracavity heat spreader. With the intracavity heat spreader, the output power and slope efficiency are 7.6 W and 42.2%, respectively. The difference in the slope efficiency can be explained by the difference in absorption efficiency, caused by different spatial distributions of the absorbed pump light.

We investigate the effect of relative wavelength difference between material gain and resonance peaks on lasing performance in vertical-external-cavity surface-emitting lasers (VECSELs). We propose a measurement method of the wavelength-dependent modal gain profiles by inserting a birefringent filter inside a cavity in order to modulate the optical loss according to the wavelength. With knowledge of the detailed gain profiles, we achieve a stable green output power of 3.3 W and a power conversion efficiency (= green output power/pump input power) of 17% in VECSEL with a LiB3O5 crystal as an intracavity frequency doubler

We present a promising method to achieve a high-performance GaInNAs quantum-well (QW) laser emitting 1.36 /spl mu/m by metal-organic vapor phase epitaxy. It was found that the insertion of GaNAs-InGaAs layers to GaInNAs QW-GaAs barrier is very effective to control the emission wavelength and improve the optical property of QW. As the thickness of the GaNAs and InGaAs layers was decreased, the wavelength emitted from QW became longer. The optical efficiencies of the proposed QW structure were confirmed by the lasing performance in edge-emitting laser. The threshold current density and slope efficiency per facet of a 1360-nm laser diode are measured to be 892 A/cm/sup 2/ and 0.135 W/A, respectively.

As pixel size of image sensors shrinks down rapidly, we are reaching technical barrier to get the required low light performance. In this paper, recent advanced technologies such as backside illumination, new color filter array, low F-number with extended depth of field technologies, etc. are introduced to overcome such a barrier. It is shown that the integration of these advanced sensor technologies can make pixel size shrink down toward 1.0 mum with the required performance.

We report on the development and demonstration of the watt-level operation of a compact green vertical external cavity surface emitting laser optically end-pumped by a single chip laser diode without any focusing lenses.

We analyzed the effect of heat-spreader location on lasing properties of newly devised end-pumped vertical-external-cavity surface-emitting lasers in terms of the dissimilar behavior of pump beam redirection scheme and thermal lens effect.

In this report, we present the improved optical pumping efficiency in vertical external cavity surface emitting laser through the recycling the wasted pumping energy by employing the double band DBR which highly reflects a pump beam as well as a lasing one

We present the theory of intracavity optical second harmonic generation in VECSELs with well-known semiconductor laser rate equations. The theory is also included phase mismatching terms, which affects the nonlinearity available for the interaction.

There is provided an end-pumped vertical external cavity surface emitting laser (VECSEL) in which a pump laser beam is incident on a laser chip at a right angle. In the external cavity surface emitting laser, a laser chip package is provided with a laser chip emitting light at a first wavelength by optical pumping, an external mirror is spaced apart from a top surface of the laser chip package to transmit a portion of the light emitted from the laser chip to the outside and to reflect the remainder to the laser chip, a heat sink is coupled to the bottom surface of the laser chip package to discharge heat generated by the laser chip, and a pump laser faces a bottom surface of the heat sink to emit pump light at a second wavelength perpendicular to the laser chip.

We have optimized a resonant gain structure of a 920 nm vertical external cavity surface emitting laser. We found that a long saturated carrier lifetime in shallow quantum well (QW) under a high injection level restricts the laser performance. An insertion of non-absorbing laser in the middle of barrier layers with multi QWs is effective to reduce the saturated carrier lifetime and, therefore, to enhance the laser performance. With the optimized laser structure, which has 10 periods of triple In 0.09 Ga 0.91 As QWs located at the anti-standing wave optical field with A l0.3 Ga 0.7 As non-absorbing layers in the middle of GaAs barrier, we achieved 4.9 W operation at 920nm. Subsequently blue laser was achieved by employing an intra-cavity frequency doubling crystal LBO. As a result, we demonstrated 2 W single transverse mode operation in blue (460 nm) with a 20 W pump laser power. The conversion efficiency from 808 nm pump laser to the blue laser is measured to be 10 %.

A measurement method of resonantly enhanced gain profiles in vertical-external-cavity surface-emitting lasers is developed. By applying the method with LBO as intra-cavity frequency doubler, a second-harmonic-generation efficiency of 15% and a stable output power of 2 W are realized.

SCH-SQW InGaAsP/InGaP lasers emitting at 809 nm were made by liquid phase epitaxy technique. The lasers are very economical and simple to operate, and reliably pump a Nd:YAG green laser. The resultant output power at /spl lambda/=532 nm was near 30 mW in a stable and single lobe. >

Spot size converter (SSC)-SOA consists of a slightly tensile bulk 0.2 /spl mu/m thick InGaAsP (/spl lambda/=1.55 /spl mu/m) active layer and 0.1 /spl mu/m thick InGaAsP (/spl lambda/=1.3 /spl mu/m) waveguides, which were grown by selective area growth (SAG) using MOCVD to implement SSC. The total device length is 1500 /spl mu/m. The thickness enhancement factor was greater than 3 by using SiO/sub 2/ mask. The SAG method with lateral tapering technique provided a typical beam divergences of 8/spl deg//spl times/15/spl deg/. To reduce facet reflectivity, window regions of 20 /spl mu/m length were introduced and the waveguides were tilted by 7/spl deg/. Both facets were antireflection coated to minimize the reflection from the cleaved facet. The gain measurement was done by coupling lensed fibers to both sides. To obtain the higher coupling efficiency in SOA module, taper lensed fiber with AR coating were used. Larger than 22 dB of the fiber to fiber gain was obtained for -20 dBm input power and 150 mA at 1540 nm.

We investigate the effect of the properties of an intracavity diamond heat spreader on the lasing performance of vertical-external-cavity surface-emitting lasers. We compared two intracavity diamonds with different average birefringences. When a polarization selective element is inserted into the cavity, the infrared output powers are reduced by 13% and 7%, respectively, for the samples with higher and lower average birefringences. The pump-power limited maximum green output powers were changed from 3to5.2W by rotating the samples with lower average birefringence. In order to explain the variation in green output power, the additional round-trip loss caused by diamond birefringence was analyzed theoretically and experimentally. We found that the loss can be reduced when axes of the birefringence are aligned to the axes of the polarization selective element.

We report on the demonstration of highly efficient blue lasers based on intracavity frequency doubling vertical-external-cavity surface-emitting lasers (VECSELs). By optimizing the number of InGaAs quantum wells and employing Al0.3Ga0.7As carrier blocking layers in resonant periodic gain structures, we observed the pump-power-limited output power of 4.5W at 920nm for an InGaAs∕GaAs quantum well VECSEL. With a frequency doubling LiB3O5 crystal inside the cavity, 1.9W continuous-wave 460nm blue output was demonstrated. Power conversion efficiencies (=output power∕pump input power) of 22.5% and 9.5% are realized for λ∼920nm and λ∼460nm, respectively.

The authors report on the development and demonstration of the high power operation of optically end-pumped vertical external cavity surface emitting laser devices emitting at 532 and 460nm. 2.7W green and 1.4W blue output powers were achieved with a good beam quality by intracavity frequency doubling with second harmonic generation crystal. High efficiency and good beam quality are attributed to the enhanced thermal management by the diamond heat spreader directly bonded to the gain region and effective optical pumping by placing the pump laser diode behind the laser structure.

The authors have optimized a resonant gain structure of a 920nm vertical external cavity surface emitting laser. They found that long saturated carrier lifetime in shallow quantum well (QW) under a high injection level restricted the laser performance. An insertion of nonabsorbing layer in the middle of barrier layers with multi-QWs was very effective to reduce the saturated carrier lifetime and, therefore, to enhance the laser performance. With the optimized gain structure, which had ten periods of triple InGaAs QWs with Al0.3Ga0.7As nonabsorbing layers in the middle of GaAs barriers, they achieved 4.9W output power at 10°C.