High-power tapered diode lasers utilizing monolithic gratings

Semiconductor lasers are small and robust devices with low power consumption and good reliability. They can be produced in a wafer scale process yielding up to thousands of devices and a large span of wavelengths can be covered with different structures. Applications, such as Raman spectroscopy with large excitation areas, seed lasers for non-linear frequency conversion and pumping solid state and fiber lasers, require the combination of high output power, narrow emission linewidth operation and good beam quality. The combination of these demanding requirements can be fulfilled using tapered diode lasers with monolithic gratings. Tapered amplifier diodes provide high output powers while maintaining good beam quality. Narrow emission linewidth can be achieved using a wavelength selective distributed Bragg reflector structure (DBR). Using a narrow linewidth DBR laser as a master oscillator (MO) and a tapered amplifier as the power amplifier (PA) enables the combination of high output power, narrow emission linewidth and good beam quality. When these structures are monolithically integrated on a semiconductor chip, the advantages of compact and simple configuration and a scalable process are maintained. The tapered amplifier section amplifies any backward reflected light and couples back to the master oscillator, broadening the emission linewidth. For applications such as atomic physics, this broadening can be eliminated by placing an optical isolator between the master oscillator and power amplifier. In this paper we present key laser characteristics of DBR MOPA lasers produced at Modulight, both as a monolithic structure and as separate components. The fabricated devices operate in the 78xnm region to fit wavelength requirements for Raman spectroscopy (785nm) and rubidium (778nm, 780nm) applications, as well as at 935nm for ytterbium ion repumping. The concept and process can be adapted to the whole emission band available from GaAs based lasers.