KEYWORDS: Quantum wells, Laser development, Quantum dots, High power lasers, Laser stabilization, Semiconductor lasers, Near field optics, Temperature metrology, Continuous wave operation
Reliable, high power laser diodes at 980 nm are the essential devices for pumping Er or Er/Yb doped fibre amplifiers. Applications where a high fibre coupling efficiency is required, demand lasers with high spatial beam quality. Tapered lasers are today one of the most interesting solution in terms of high brightness (high power with high spatial beam quality). Furthermore, a reduced temperature shift of the wavelength is important for high power optical pump applications because this implies a less stringent temperature control. New GaInAs/(Al)GaAs quantum-dot materials exhibit a high wavelength stability vs. current and temperature. Using these quantum dots as active region, we have developed index guided tapered diode laser with a small aperture (width less than 30 μm) and standard AR/HR coatings. This device showed an optical power of 1 W CW at 1.6 A at 980 nm with a M2 factor of 2.9 in the slow axis. Furthermore, we have measured a wavelength variation of 0.0075 Å/mA at 20°C with current and 1.7 Å/°C with temperature, which is weaker than typical variations of quantum well lasers. We also developed an array of seven quantum-dot lasers which emits 3 W CW at 5.7 A. Quantum well individual devices, using the same confinement layers and waveguide geometry were also developed for comparison.
Er or Er/Yb doped fibre amplifiers are key components for high bit rate, WDM, networks. Reliable, high power laser diodes at 980nm are the essential devices for pumping these amplifiers. Applications where a high fibre coupling efficiency is required, demand lasers with high spatial beam quality, a property not inherent to broad area multimode lasers. Tapered lasers are today one of the most interesting solution in terms of high brightness (high power with high spatial beam quality). Furthermore, a reduced temperature shift of the emission wavelength is important for high power optical pump applications because this implies a less stringent temperature control for wavelength adjustment. New GaInAs/(Al)GaAs quantum dot materials exhibit a high wavelength stability vs. current and temperature. Combining these quantum dots as active region and tapered waveguide, we have developed tapered laser diodes with standard AR/HR coatings. This devices showed high optical powers at 980nm with low M2 factors in the slow axis. Furthermore, we have measured very low wavelength variations at 20°C with current and with temperature, which is weaker than typical wavelength variations of quantum well lasers.
Laser diodes at 980 nm have important applications in medicine (surgery, dentistry) and Telecoms for WDM, high bit rate networks (Er or Er/Yb doped fibre amplifiers). These applications need a high coupling efficiency of the source into a fibre. High brightness mini-bars with an emissive length of 2.7 mm have been recently developed. These devices consist of an array of aluminium free active region index guided tapered laser diodes with standard AR/HR coatings. We have improved the performances as a result of a new epitaxial layer and a new mini-bar design. We measure an optical output power of 25W at 40A under CW operation at 15°C. At 25°C and 33A, we obtain 20W CW and the far field along the slow axis has a Gaussian shape, with a low FWHM value of 3.5°. Along the fast axis, the far-field also has a Gaussian shape and a FWHM of 31,5°. To couple this tapered diode laser mini-bar into a 100μm diameter fibre (0.26 numerical aperture), we use a patented collective beam shaping technique for optical coupling. We obtain a coupled power of 11.2W under CW operation at 971 nm, 21°C with an emitted power from the mini-bar of 21.7W, resulting in a coupling efficiency of 52%. The conductively cooled mini-bar, all the optics and the optical fibre connector are assembled into a 82x62x23mm package. To our knowledge this is the highest reported power coupled into 100μm optical fibre from a single laser diode chip using a collective coupling scheme without any array of micro-optics.
KEYWORDS: Semiconductor lasers, High power lasers, Near field, Laser dentistry, Continuous wave operation, Laser vision correction, Near field optics, Monochromatic aberrations, Laser development, Diodes
High bit-rate, WDM, networks are reliant on Er or Er/Yb doped fiber amplifiers. Reliable, high power laser diodes at 980nm and 1480nm are key devices for pumping these amplifiers. We have developed several 980 nm laser diode structures at 980 nm, using an Aluminum free active region and standard AR/HR coatings on the facets. Our laser show low optical losses, low threshold current density and a high external differential efficiency. We demonstrate a mini-bar of small angle index guided tapered laser diodes (emissive width of 3 mm) with an optical output power of 20W at 33A under CW operation (25°C). The far field of the slow axis has a Gaussian single lobed shape, with a FWHM of 3.5° at maximum power, which is two times less than obtained with multimode broad area lasers. With such a device, we expect to couple 10W into a 100μm diameter fiber. We also demonstrate a large aperature gain-guided tapered laser with an output power of 2.4W and a calculated M21/c2 = 3, the M21/c2 factor being calculated with the method based on measurements of the fields profiles widths at 1/c2.
High bit rate, WDM, networks use intensively Er or Er/Yb doped fibre amplifiers. Reliable, high power laser diodes at 980nm and 1480nm are key devices for pumping these amplifiers. We have developed different structures of laser diodes at 980nm, using Aluminium free materials. Our laser structure shows low optical losses together with a low threshold current density and a high external differential efficiency. We demonstrate a mini-bar of broad area laser diodes (emissive width of 2.6mm) with an optical output power of 19W at 25A under CW operation. We have also developed a mini-bar of small angle index guided tapered laser diodes (W=2.6mm). We demonstrate 17W at 27.6A under CW operation at 20 degree(s)C. Slow axis far field has a Gaussian single mode shape, with a FWHM of 3.3 degree(s) (at 15A, 11W), which is two times less than obtained on multimode broad area lasers. With such a device, we expect to couple 10W into a 100micrometers diameter fiber. We also demonstrate, on a large aperture gain-guided tapered laser, an output power of 1.3W with an M2 of 3.3
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