Fiber coupled diode lasers are widely used in many fields now especially as pumps in fiber laser systems. In many fiber laser applications, high brightness pumps are essential to achieve high brightness fiber lasers. Furthermore, 976nm wavelength absorption band is narrow with Yb3+ doped fiber lasers which is more challenging for controlling wavelength stabilized in diode laser modules. This study designed and implemented commercial available high brightness and narrow wavelength width lasers to be able to use in previous mentioned applications. Base on multiple single emitters using spatial and polarization beam combining as well as fiber coupling techniques, we report a wavelength stabilized, 105μm NA 0.15 fiber coupled diode laser package with 100W of optical output power at 976 nm, which are 14 emitters inside each multiple single emitter module. The emitting aperture of the combined lasers output are designed and optimized for coupling light into a 105μm core NA 0.15 fiber. Volume Bragg grating technology has been used to improve spectral characteristics of high-power diode lasers. Mechanical modular design and thermal simulation are carried out to optimize the package. The spectral width is roughly 0.5 nm (FWHM) and the wavelength shift per °C < 0.02nm. The output spectrum is narrowed and wavelength is stabilized using Volume Bragg gratings (VBGs). The high brightness package has an electrical to optical efficiency better than 45% and power enclosure more than 90% within NA 0.12. Qualification tests have been included on this kind of package. Mechanical shock, vibration and accelerated aging tests show that the package is reliability and the MTTF is calculated to be more than 100k hours at 25°C.
Proc. SPIE. 9733, High-Power Diode Laser Technology and Applications XIV
KEYWORDS: Energy efficiency, Diffraction, Mirrors, Polarization, High power lasers, Reflectivity, Semiconductor lasers, Collimation, High power fiber lasers, Beam shaping, Electro optics, Diffraction gratings
Spectral beam combination expands the output power while keeps the beam quality of the combined beam almost the same as that of a single emitter. Spectral beam combination has been successfully achieved for high power fiber lasers, diode laser arrays and diode laser stacks. We have recently achieved the spectral beam combination of multiple single emitter diode lasers. Spatial beam combination and beam transformation are employed before beams from 25 single emitter diode lasers can be spectrally combined. An average output power about 220W, a spectral bandwidth less than 9 nm (95% energy), a beam quality similar to that of a single emitter and electro-optical conversion efficiency over 46% are achieved.
In this paper, Rigorous Coupled Wave analysis is used to numerically evaluate the influence of emitter width, emitter pitch and focal length of transform lens on diffraction efficiency of the grating and spectral bandwidth.
To assess the chance of catastrophic optical mirror damage (COMD), the optical power in the internal cavity of a free running emitter and the optical power in the grating external cavity of a wavelength locked emitter are theoretically analyzed.
Advantages and disadvantages of spectral beam combination are concluded.
In this study，the chip bonding processes for various chips from various chip suppliers around the world have been
optimized to achieve reliable chip on sub-mount for high performance. These chip on sub-mounts, for examples, includes
three types of bonding, 8xx nm-1.2W/10.0W Indium bonded lasers, 9xx nm 10W-20W AuSn bonded lasers and 1470 nm
6W Indium bonded lasers will be reported below. The MTTF@25℃ of 9xx nm chip on sub-mount (COS) is calculated
to be more than 203,896 hours. These chips from various chip suppliers are packaged into many multiple single emitter
laser modules, using similar packaging techniques from 2 emitters per module to up to 7 emitters per module. A
reliability study including aging test is performed on those multiple single emitter laser modules. With research team’s 12
years’ experienced packaging design and techniques, precise optical and fiber alignment processes and superior chip
bonding capability, we have achieved a total MTTF exceeding 177,710 hours of life time with 60% confidence level for
those multiple single emitter laser modules. Furthermore, a separated reliability study on wavelength stabilized laser
modules have shown this wavelength stabilized module packaging process is reliable as well.
We developed a high brightness fiber coupled diode laser module providing more than 140W output power from a
105μm NA 0.15 fiber at the wavelength of 915nm.The high brightness module has an electrical to optical efficiency
better than 45% and power enclosure more than 90% within NA 0.13. It is based on multi-single emitters using optical
and polarization beam combining and fiber coupling technique. With the similar technology, over 100W of optical power
into a 105μm NA 0.15 fiber at 976nm is also achieved which can be compatible with the volume Bragg gratings to
receive narrow and stabilized spectral linewidth. The light within NA 0.12 is approximately 92%.
The reliability test data of single and multiple single emitter laser module under high optical load are also presented and
analyzed using a reliability model with an emitting aperture optimized for coupling into 105μm core fiber. The total
MTTF shows exceeding 100,000 hours within 60% confidence level. The packaging processes and optical design are
ready for commercial volume production.