A single ridge waveguide laser wavelength stabilized by a compact external Bragg grating cavity with an output power as much as 380 mW and a beam quality factor M 2 of 1.3 is presented. A characterization concerning tunability by current, short-term optical linewidth and intensity fluctuations is performed. The device exhibits a wavelength tuning factor at 780 nm of 0.5 pm/mA, a short-term optical linewidth of 18 kHz and a low-frequency RIN of -136 dB/Hz. These characteristics allow a high resolution absorption spectroscopy of the D2 line of rubidium.E XTERNAL cavity diode lasers (ECDLs) operating in the near infra-red spectral range became a standard tool in the field of atomic physics as well as in bio-medical applications. This is due to a narrow linewidth [1], precise frequency selectability, high power in the order of 100 mW as well as the excellent side mode suppression of 50 dB and higher of ECDLs. They are applied for atom cooling and trapping [2], [3], high precision spectroscopy for establishing laser optical frequency standards [4], quantum information and Raman spectroscopy [5]. However, advanced applications require a narrow linewidth below 100 kHz as well as high output power on the several hundred mW regime [6]. Furthermore, applications of conventional ECDLs in Littrow [7] as well as in Littman/Metcalf [8] configuration suffer from their sensitivity on ambient conditions as there are vibrations, acoustics, and temperature variations. Approaches via Distributed Bragg Reflector (DBR) structures [9] as well as via Volume Holographic Gratings (VHGs) [10], [11] have been chosen for overcoming these issues of conventional ECDLs and Distributed Feedback (DFB) lasers [12].VHGs consisting of photo-thermo-refractive glass with a high damage threshold, however, have proven to be able to simplify external-cavity configurations [13]. Placing a reflective VHG in front of the laser diode with the grating period perpendicular to the light propagation helps minimize the packaging size. This VHG-based external cavity design is a convenient means used to stabilize high-power arrays of broad area [14] or tapered [15] diode lasers. Such high power ECDLs have been applied for rubidium (Rb) laser pumping at 780 nm [16] and optical pumping of delta oxygen at 763.8 nm [17]. Regardless of the high output power of these diode laser arrays, they can hardly be used for high-precision manipulation of atoms and particles since they suffer from a broad spectral linewidth and a non-Gaussian, low-brightness beam profile with a poor spatial coherence.In this document we investigate an easy-to-use, compactly packaged VHG stabilized single ridge waveguide laser with a S. Rauch and J. Sacher are with Sacher Lasertechnik,

Typical for broad-area laser (BAL) diodes operating in a continuous-wave mode is a narrowing of the near-field (NF) width at the output facet for high injection currents (output powers). This phenomenon increases the facet load of BALs, resulting in a reduction in the level of catastrophic optical mirror damage. In this letter, we demonstrate theoretically that thermally induced changes in the refractive index in both lateral and longitudinal directions not only cause the NF narrowing at the front facet but also a broadening of the NF at the back facet. In contrast, a sole lateral self-heating induced variation in the refractive index (commonly referred to as thermal lensing) does not result in a NF narrowing. Our theoretical findings are confirmed by measurements of the current-dependent profiles of the NF at the back and front facets of a BAL with a stripe width of 120 μm emitting at 960 nm. Furthermore, our quasi three-dimensional thermo-electro-optic simulations indicate that a longitudinally homogeneous device temperature can reduce the front-facet load while keeping the beam quality unchanged compared with the experimental results.

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