Room-Temperature Operation of Optically Pumped Blue-Violet GaN-Based Vertical-Cavity Surface-Emitting Lasers Fabricated by Laser Lift-Off

Chu, Jhih‐Wei; Lu, Tien−Chang; Yao, H. H.; Kao, Chih−Chiang; Liang, W.; Tsai, J. Y.; Kuo, Hao‐Chung; Wang, Shingchung

doi:10.1143/jjap.45.2556

Cited by 40 publications

(21 citation statements)

References 10 publications

(23 reference statements)

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“…[22] These results thus show that the bosonic excitonpolaritons in GaN which form a phase-coherent state above a characteristic density, exhibit spontaneous symmetry breaking above 300K. This contrasts to linear polarisation seen in all previous systems (including both InP-based [23] and similar GaN-based [24] bulk VCSELs), and is directly observed through the polarisation of light emitted by polaritons. The coherent polariton state thus fulfils all the criteria to be classed as a Bose-Einstein condensate.…”

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confidence: 64%

Spontaneous Polarization Buildup in a Room-Temperature Polariton Laser

et al. 2008

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We observe the build up of strong (∼50%) spontaneous vector polarisation in emission from a GaN-based polariton laser excited by short optical pulses at room temperature. The Stokes vector of emitted light changes its orientation randomly from one excitation pulse to another, so that the timeintegrated polarisation remains zero. This behaviour is completely different to any previous laser. We interpret this observation in terms of the spontaneous symmetry breaking in a Bose-Einstein condensate of exciton-polaritons.PACS numbers: 71.36.+c, 03.75.Kk, Polariton lasers are coherent light sources based on emission of light from a coherent ensemble of excitonpolaritons -the mixed light-exciton quasiparticles in semiconductor microcavities. The concept of polariton lasing was first proposed in 1996 [1], followed a few years later by reports of coherent polariton emission in microcavities [2,3,4]. Recently, we reported polariton lasing at room temperature in GaN-based microcavities [5]. Apart from being very promising for applications, the concept of polariton lasing involves several fundamental physics issues. Contrary to conventional lasers, polariton lasers emit coherent and monochromatic light spontaneously. This is achieved when mixed light-matter quasiparticles (exciton-polaritons), Bosecondense inside a semiconductor microcavity. BoseEinstein condensation (BEC) of the polaritons is a subject of intense experimental and theoretical research at present. Several experimental works claiming polariton BEC have appeared recently [6,7,8]. Though polariton BEC implies polariton lasing these two phenomena are not identical. For polariton lasing a macroscopically populated quantum state of exciton polaritons must be created, which can be considered as a polariton condensate. Polariton lasing does not require thermal equilibrium in the system or the spontaneous build-up of the order parameter, which are the main criteria for BEC when understood as a thermodynamic phase transition. Which experimental measurement should be considered as decisive proof for the exciton-polariton BEC is still a subject of debate within the community. Thermalisation of the exciton-polaritons detected by angle-resolved photoluminescence (PL) measurements has been considered one of the key criteria for a long time [6,7]. However, a similar angular dependence of the PL has also been observed in GaAs-based photon lasers [9]. The spatial coherence of polariton emission demonstrated in Ref.[6] is characteristic for conventional lasers as well. Recent theoretical work suggests that observation of the spontaneous buildup of the vector polarisation in emission from polariton lasers would be evidence for the spontaneous symmetry breaking in the system [10,11,12]. In turn, spontaneous symmetry breaking is considered to be a smoking gun for BEC ever since the pioneering work of Goldstone [13,14].Here we report observations of the build up of the spontaneous vector polarization at room temperature in bulk GaN microcavities. Unlike the recent low temperature e...

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confidence: 64%

Spontaneous Polarization Buildup in a Room-Temperature Polariton Laser

et al. 2008

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“…The large refractive index contrast in dielectric materials can provide high-reflectivity and large-stopband DBRs with less number of pairs. The drawbacks of the double dielectric DBR VCSEL are the difficulty of controlling the cavity thickness precisely and the complicated fabrication process due to the employment of laser lift-off technique [26]. In addition, the GaN cavity should be kept as thick as possible to avoid the damage of the InGaN/GaN MQWs during the laser lift-off process.…”

Section: Difficulty In Fabrication Of Nitride-based Vcselmentioning

confidence: 99%

“…Our approaches to the realization of GaN-based VCSELs are mainly based on the double dielectric DBR VCSELs and the hybrid DBR VCSELs. The lasing action in double dielectric VCSEL has been demonstrated by optical excitation in our previous studies [26], [27]. To achieve electrically pumped GaN-based VCSELs, we focus our study on the structure of hybrid DBR VCSELs in recent years.…”

Section: Difficulty In Fabrication Of Nitride-based Vcselmentioning

confidence: 99%

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Development of GaN-Based Vertical-Cavity Surface-Emitting Lasers

Chen

et al. 2009

IEEE J. Select. Topics Quantum Electron.

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Abstract-This paper reviews the fabrication technology and performance characteristics of optically pumped and electrically pumped GaN-based vertical-cavity surface-emitting lasers (VCSELs). The lasing action of optically pumped hybrid GaNbased VCSELs has been observed at room temperature due to the employment of high-quality and high-reflectivity AlN/GaN-based distributed Bragg reflectors in the VCSEL structure. Based on the device structure of the optically pumped hybrid GaN-based VCSELs, we further achieved the lasing action of electrically pumped GaN-based VCSELs under continuous-wave operation at 77 K. The laser has a threshold injection current of 1.4 mA and emits a blue wavelength at 462 nm together with a narrow linewidth of about 0.15 nm. The laser beam has a divergence angle of about 11.7• with a polarization ratio of 80%. A very strong spontaneous coupling efficiency of 7.5 × 10 −2 was measured.Index Terms-Distributed Bragg reflector (DBR), GaN, electrical pumping, superlattice, vertical-cavity surface-emitting laser (VCSEL).

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“…Because of their particular advantages over edge emitting lasers such as light emission in the vertical direction, circular beam shape, and the possibility to fabricate dense arrays, much effort was dedicated to the development of GaN-based VCSELs [3][4][5][6][7][8][9]. The essential problem in the VCSEL is the focusing of the carrier density in the center of device due to the optical mode confinement in this issue.…”

Section: Introductionmentioning

confidence: 99%