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A wavelength adjustable distributed Bragg reflector diode laser suitable for background-free Raman spectroscopy at 785 nm is presented. It is based on a GaAsP single quantum well embedded in a 1 μm thick AlGaAs waveguide. The 3 mm long device consists of a 2.2 μm wide ridge waveguide and a 10th order DBR surface grating as wavelength selective rear side mirror. On-chip resistors implemented as heater elements next to the grating allow applying a current that enables a flexible wavelength adjustment by Joule heating. At a heatsink temperature of 25°C, the laser provides 100 mW of optical output power and narrowband laser emission with spectral widths of 20 pm (0.3 cm-1) along the whole power range. A current up to 0.6 A applied to the on-chip resistors shifts the excitation wavelength by 2.18 nm (35 cm-1) with narrowband emission at all settings and an optical output power remaining within a span of 14 mW. Along that available wavelength range, alternating dual-wavelength operations for five wavelengths separated from another by about 8 cm-1 are presented (f = 1 Hz, 50% duty cycle). At 50 ms after switching, the spectral distance between selected target wavelengths and measured peak wavelengths is ≤ 1.1 cm-1 (≤ 0.07 nm). This enables flexible selections of excitation wavelengths with low latencies for background-free Raman spectroscopy.
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