Watt-class high-power, high-beam-quality photonic-crystal lasers

Journal name:
Nature Photonics
Volume:
8,
Pages:
406–411
Year published:
DOI:
doi:10.1038/nphoton.2014.75
Received
Accepted
Published online

Abstract

The applications of surface-emitting lasers, in particular vertical-cavity surface-emitting lasers (VCSELs), are currently being extended to various low-power fields including communications and interconnections. However, the fundamental difficulties in increasing their output power by more than several milliwatts while maintaining single-mode operation prevent their application in high-power fields such as material processing, laser medicine and nonlinear optics, despite their advantageous properties of circular beams, the absence of catastrophic optical damage, and their suitability for two-dimensional integration. Here, we demonstrate watt-class high-power, single-mode operation by a two-dimensional photonic-crystal surface-emitting laser under room-temperature, continuous-wave conditions. The two-dimensional band-edge resonant effect of a photonic crystal formed by metal–organic chemical vapour deposition enables a 1,000 times broader coherent-oscillation area, which results in a high beam quality of M2 ≤ 1.1, narrowing the focus spot by two orders of magnitude compared to VCSELs. Our demonstration promises to realize innovative high-power applications for surface-emitting lasers.

At a glance

Figures

  1. Schematic of the PCSEL structure and SEM images of a PC.
    Figure 1: Schematic of the PCSEL structure and SEM images of a PC.

    a, Schematic of the PCSEL structure. Arrows indicate the growth direction of the first epitaxial and regrowth structures. b, Top-view SEM image of the fabricated square-lattice PC before burial by MOCVD regrowth. The lattice constant is a = 287 nm. c, Cross-sectional SEM image of PC air holes in the x-direction after burial. Note that the roughened portions were introduced when the sample was cleaved for SEM observation.

  2. Lasing a characteristics of a PCSEL operated under room-temperature pulsed conditions.
    Figure 2: Lasing a characteristics of a PCSEL operated under room-temperature pulsed conditions.

    a, Output power versus current. b, Lasing spectrum measured through a single-mode fibre with a current of 280 mA. A rather short pulse width of 50 ns was used to suppress the thermal broadening of the spectrum during current injection. c, Current dependence of FFP. Narrow beam divergence is maintained with FWHM < 1° up to 5 A.

  3. Lasing characteristics of a PCSEL operated under room-temperature c.w. conditions.
    Figure 3: Lasing characteristics of a PCSEL operated under room-temperature c.w. conditions.

    a, Light–current–voltage characteristics for operation at 20 °C. b, Lasing spectrum measured through single-mode fibre at 300 mA. c, Current dependence of FFP. The beam has FWHM < 3° up to 2.5 A. An increase in beam divergence is observed above 1.0 A. d, Beam radius versus position of focusing along axis z under operation at 0.9 A and 1.0 A at 25 °C. M2 is evaluated by fitting (black and red lines) the experimental data (black circles and red squares). Black and red colours represent the x- and y-directions, respectively. e, Photograph taken immediately after direct radiation of the PCSEL on a sheet of black paper placed 8.5 cm from the PCSEL. The operation current was 1.7 A under c.w. conditions at 25 °C, giving a power of 0.86 W and an estimated power density of 11 W cm−2.

  4. Theoretical analysis and comparison with experiment.
    Figure 4: Theoretical analysis and comparison with experiment.

    a, Band structure measured well below threshold current. The lasing spectrum (right-hand panel) was measured in the surface-normal direction by injecting current above threshold, indicating that single-mode lasing occurs at band-edge B. b, Calculated mode frequencies and threshold gains of individual band-edge modes A–D. The high thresholds of modes C and D are scaled for clarity. c, Measured FFP and polarization profiles in four typical directions (polarization direction is indicated by angle θ, as defined in the upper inset). d, Calculated FFP and polarization profiles. e, Comparison of measured and calculated peak intensities of polarized components.

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Author information

  1. These authors contributed equally to this work

    • Kazuyoshi Hirose &
    • Yong Liang

Affiliations

  1. Material Research Group, Central Research Laboratory, Hamamatsu Photonics K.K., Shizuoka 434-8601, Japan

    • Kazuyoshi Hirose,
    • Yoshitaka Kurosaka,
    • Akiyoshi Watanabe &
    • Takahiro Sugiyama
  2. Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510, Japan

    • Kazuyoshi Hirose,
    • Yong Liang,
    • Yoshitaka Kurosaka &
    • Susumu Noda
  3. JST ACCEL, Kyoto University, Kyoto 615-8510, Japan

    • Susumu Noda

Contributions

S.N. directed the work. K.H. fabricated the device with T.S., and performed the experiments with A.W. Y.L. conducted the theoretical analysis of the device. Y.K. measured the band structure of the device. K.H. and Y.L. wrote the manuscript with S.N.

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The authors declare no competing financial interests.

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