Abstract
To obtain high-power semiconductor lasers with stable operation in a single longitudinal mode and improve the characteristics of the output beam, an end-emitting surface second-order metal grating distributed feedback (DFB) laser emitting at around 940 nm is fabricated. The characteristics of the uncoated devices with and without gratings are tested under room temperature continuous-wave conditions without any temperature-control device and compared. The devices with gratings achieve high powers of up to 385 mW/facet and a small lateral far-field angle of 2.7° at 1.5 A, have only 4.13 nm/A wavelength-shift, and 0.09 nm spectral linewidth at 600 mA, and operate in a stable longitudinal mode. Devices without gratings operate in multimode, with a larger lateral far-field angle (7.3°) and spectral linewidth (1.3 nm), although with higher output powers. Because of the integration of second-order metal gratings and their very high coupling capability, the output beam quality is improved greatly, the lasing wavelength is stable and varies slowly with changes in injection current, while the spectrum is narrowed dramatically, and the far-field angles are greatly reduced. This opens the way for the realization of watt-scale power broad-stripe (>100 μm) surface second-order metal grating end and surface-emitting DFB lasers and arrays with single frequency, single mode operation and high output beam quality.
Highlights
To obtain high-power semiconductor lasers with stable operation in a single longitudinal mode and improve the characteristics of the output beam, an end-emitting surface second-order metal grating distributed feedback (DFB) laser emitting at around 940 nm is fabricated
Because of the integration of second-order metal gratings and their very high coupling capability, the output beam quality is improved greatly, the lasing wavelength is stable and varies slowly with changes in injection current, while the spectrum is narrowed dramatically, and the far-field angles are greatly reduced. This opens the way for the realization of watt-scale power broad-stripe (>100 m) surface secondorder metal grating end and surface-emitting DFB lasers and arrays with single frequency, single mode operation and high output beam quality
Several approaches have been used to stabilize the emission wavelength, narrow the spectrum and improve the output beam quality of these pump lasers, all of which were based on establishing spectrally selective feedback, such as the combination of an external collimation lens and a volume Bragg grating (VBG) [2,3,4], external fiber Bragg gratings (FBG) [5,6,7,8,9,10] and distributed feedback gratings integrated into the laser chip (DFB laser) [11,12,13]
Summary
To obtain high-power semiconductor lasers with stable operation in a single longitudinal mode and improve the characteristics of the output beam, an end-emitting surface second-order metal grating distributed feedback (DFB) laser emitting at around 940 nm is fabricated. The devices with gratings achieve high powers of up to 385 mW/facet and a small lateral far-field angle of 2.7° at 1.5 A, have only 4.13 nm/A wavelength-shift, and 0.09 nm spectral linewidth at 600 mA, and operate in a stable longitudinal mode.
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