The Experts below are selected from a list of 3048 Experts worldwide ranked by ideXlab platform
Toshihiko Baba - One of the best experts on this subject based on the ideXlab platform.
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low threshold lasing and purcell effect in microdisk lasers at room temperature
IEEE Journal of Selected Topics in Quantum Electronics, 2003Co-Authors: Toshihiko Baba, D SanoAbstract:In this paper, we discuss the Purcell effect, which enhances the Spontaneous Emission rate, in microdisk lasers operating at room temperature by continuous wave photopumping. We theoretically analyzed the Purcell effect at room temperature by using the four-level rate equations that include the intraband relaxation and the nonradiative effect. We also fabricated 1.55-/spl mu/m GaInAsP microdisk lasers with a minimum diameter of 1.7 /spl mu/m and a minimum threshold power of 19 /spl mu/W. Then, we measured the carrier lifetime in a 2.6-/spl mu/m-diameter device by the phase-resolved spectroscopy method, and confirmed that the carrier lifetime was shortened to 1/10 of that in the as-grown epitaxial wafer at a low pump level. From the comparison between the theory and the experiment, we estimated the Purcell Factor to be 6.7, the Spontaneous Emission Factor to be 0.11, and the nonradiative lifetime to be 4 ns. The nonradiative lifetime was consistent with that estimated by another methods. We believe that this is the first demonstration of the Purcell effect in semiconductor microcavities at room temperature.
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proposal and finite difference time domain simulation of whispering gallery mode microgear cavity
IEEE Journal of Quantum Electronics, 2001Co-Authors: Masayuki Fujita, Toshihiko BabaAbstract:The existence of many high Q whispering gallery modes in microdisk and microcylinder lasers seriously affects the internal efficiency in lasing operation and disturbs the enhancement of the Spontaneous Emission Factor. To suppress these modes except for one lasing mode, we propose the microgear cavity having a grating with the same period as that of the mode standing wave. A finite-difference time-domain simulation theoretically demonstrates that the microgear selects one resonant mode that satisfies the unique condition regarding the mode order and the phase. This paper describes the dependence of the mode behavior on some structural parameters, and concludes that a deep grating, which seems to be possible in an experiment, allows for sufficient suppression of any types of nonlasing modes and the enhancement of the Q Factor of the lasing mode.
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Large Spontaneous Emission Factor of 0.1 in a microdisk injection laser
IEEE Photonics Technology Letters, 2001Co-Authors: R. Fujita, Reona Ushigome, Toshihiko BabaAbstract:A large Spontaneous Emission Factor of 0.1 was evaluated in a 1.56 /spl mu/m-GaInAsP microdisk injection laser operating under continuous-wave condition with a threshold current of 50 /spl mu/A. Some clear evidence of the large Spontaneous Emission Factor, i.e., superlinear light-current characteristics and nonclamped carrier-current characteristics, were observed. It was confirmed that the matching of the lasing wavelength to the Spontaneous Emission allowed larger Spontaneous Emission Factor.
Daniel Y Chu - One of the best experts on this subject based on the ideXlab platform.
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estimation of the Spontaneous Emission Factor for microdisk lasers via the approximation of whispering gallery modes
Journal of Applied Physics, 1994Co-Authors: Mee Koy Chin, Daniel Y ChuAbstract:Microdisk structures have been used to achieve low‐threshold lasing. For these microcavity lasers, the Spontaneous Emission coupling Factor β is an important parameter since it determines the threshold current of the laser. Theoretical calculation of β based on the exact solution of the modes in a microdisk is complicated. A simple, approximate method for solving the waveguide modes and the density of states is developed here, using conformal transformation and the Wentzel–Kramers–Brillouin approximation and taking into account the effect of the disk thickness. We find that the β value for a microdisk laser is smaller than that of an ideal laser that has a cylindrical waveguide structure with a strong index guiding. A considerably high value of β can still be achieved, however, in a microdisk laser.
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Spontaneous Emission from excitons in cylindrical dielectric waveguides and the Spontaneous Emission Factor of microcavity ring lasers
Journal of The Optical Society of America B-optical Physics, 1993Co-Authors: Daniel Y ChuAbstract:The modification of the Spontaneous Emission from various dipoles in a cylindrical dielectric waveguide is studied as a function of the refractive index and the radius of the waveguide. It is found that the Emission rates of the axial dipoles and the radial dipoles can be modified to enhance greatly the fraction of radial dipole Emission that goes into the guided lasing modes. The total Emission from the axial dipoles can be suppressed. This combination gives a high Spontaneous-Emission Factor β for a microcavity ring laser. Other microlaser structures that have high β values are also discussed. We conclude that microlasers based on strongly guided single-mode dielectric waveguides are promising devices for achieving high β values and low lasing thresholds.
C Parsons - One of the best experts on this subject based on the ideXlab platform.
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Spontaneous Emission Factor and its scaling in vertical cavity surface emitting lasers
Applied Physics Letters, 1994Co-Authors: Gleb Shtengel, Henryk Temkin, T Uchida, M Kim, P Brusenbach, C ParsonsAbstract:We report room‐temperature measurements of the Spontaneous Emission Factor β in high‐quality gain‐guided GaAs/AlGaAs vertical cavity surface emitting lasers. In devices with 6‐μm diameter we obtain β=2.8×10−3. The measured scaling of β with the cavity volume agrees well with classical electromagnetic model of dipole radiation. The magnitude of β exceeds that predicted by classical theory by approximately a Factor of 2.
J F Donegan - One of the best experts on this subject based on the ideXlab platform.
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fabry perot laser characterization based on the amplified Spontaneous Emission spectrum and the fourier series expansion method
IEEE Journal of Selected Topics in Quantum Electronics, 2011Co-Authors: Weihua Guo, D Byrne, Brian Corbett, J F DoneganAbstract:Comprehensive Fabry-Perot laser characterization based on measurements of the amplified Spontaneous Emission spectrum analyzed using the Fourier series expansion method is presented. The parameters of net modal gain, internal loss, quasi-Fermi level separation, linewidth enhancement Factor, injection efficiency, and geometric Spontaneous Emission Factor can all be extracted.
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technique to calculate geometric Spontaneous Emission Factor from amplified Spontaneous Emission spectrum of fp semiconductor laser
Electronics Letters, 2010Co-Authors: D Byrne, Brian Corbett, J F DoneganAbstract:The geometric Spontaneous Emission Factor is calculated from the amplified Spontaneous Emission spectrum of a Fabry-Perot (FP) laser diode. The optical loss and quasi-Fermi level separation are determined first using the Fourier transform method with the influence from the instrument response function being taken into account. From this the geometric Spontaneous Emission Factor is calculated to be 5.95 × 10 -3 just below laser threshold.
Masayuki Fujita - One of the best experts on this subject based on the ideXlab platform.
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proposal and finite difference time domain simulation of whispering gallery mode microgear cavity
IEEE Journal of Quantum Electronics, 2001Co-Authors: Masayuki Fujita, Toshihiko BabaAbstract:The existence of many high Q whispering gallery modes in microdisk and microcylinder lasers seriously affects the internal efficiency in lasing operation and disturbs the enhancement of the Spontaneous Emission Factor. To suppress these modes except for one lasing mode, we propose the microgear cavity having a grating with the same period as that of the mode standing wave. A finite-difference time-domain simulation theoretically demonstrates that the microgear selects one resonant mode that satisfies the unique condition regarding the mode order and the phase. This paper describes the dependence of the mode behavior on some structural parameters, and concludes that a deep grating, which seems to be possible in an experiment, allows for sufficient suppression of any types of nonlasing modes and the enhancement of the Q Factor of the lasing mode.
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ultrasmall and ultralow threshold gainasp inp microdisk injection lasers design fabrication lasing characteristics and Spontaneous Emission Factor
IEEE Journal of Selected Topics in Quantum Electronics, 1999Co-Authors: Masayuki Fujita, A SakaiAbstract:We have calculated lasing characteristics of current injection microdisk lasers of several microns in diameter, taking account of the scattering loss at center posts and the carrier diffusion effect. We found that the optimum width of the disk wing exposed to the air is 0.6-0.7 /spl mu/m and the minimum threshold current is nearly 10 /spl mu/A for the disk diameter of 2 /spl mu/m. The internal differential quantum efficiency can be 95% if the transparent carrier density is reduced to 7.5/spl times/10/sup 17/ cm/sup -3/ and the diffusion constant is increased to 8 cm/sup 2//s. In the experiment, we have obtained the room temperature continuous-wave operation of a GaInAsP-InP device of 3 /spl mu/m in diameter, for the first time, with a record low threshold of 150 /spl mu/A. This achievement was mainly owing to the reduction of the scattering loss at the disk edge, and hence the reduction of the threshold current density. The Spontaneous Emission Factor was estimated to be 6/spl times/10/sup -3/. This value was much reduced by the large detuning of the lasing wavelength against the Spontaneous Emission peak. A larger value over 0.1, which is expected for such a small device, will be obtained by the wavelength tuning and the narrowing of the Spontaneous Emission spectrum.