Efficient generation of 19  W yellow light by cascaded frequency doubling of a distributed Bragg reflector tapered diode

Abstract

Watt-level yellow emitting lasers are interesting for medical applications, due to their high hemoglobin absorption, and for efficient detection of certain fluorophores. In this paper, we demonstrate a compact and robust diode-based laser system in the yellow spectral range. The system generates 1.9 W of single-frequency light at 562.4 nm by cascaded single-pass frequency doubling of the 1124.8 nm emission from a distributed Bragg reflector (DBR) tapered laser diode. The absence of a free-space cavity makes the system stable over a base-plate temperature range of 30 K. At the same time, the use of a laser diode enables the modulation of the pump wavelength by controlling the drive current. This is utilized to achieve a power modulation depth above 90% for the second harmonic light, with a rise time below 40 μs.

Megahertz measurement rate wavemeter with sub-picometer resolution using second harmonic generation

“…The system can be used to gain more insight into, e.g., the wavelength behavior of low-and high power laser diodes where there is often a complex coupling between thermal, electronic and optical effects. This could be useful for achieving arbitrary on/off modulation of the second harmonic light which is needed for, e.g., medical treatments 12 .…”

Deep modulation of second-harmonic light by wavelength detuning of a laser diode

“…For longer modulation periods the temperature of the laser diode can fluctuate during the pulse making the wavelength unstable. A tailored input pulse can be used to mitigate this effect [14], but the input current pulse will then change shape depending on both the pulse length and duty cycle needed. For the system presented here the wavelength is mostly defined by the current through the DFB section that no such tailoring is needed.…”

“…SHG systems using channel waveguides in nonlinear crystals cannot be scaled to the multiple watt-level powers needed for medical treatment [13]. A 90% modulation depth of 1.5 W SH light has been achieved using wavelength detuning of DBR tapered laser diodes [14]. In this work, however, the modulation depth was limited by the mode hops of the laser.…”

Modulation of frequency doubled DFB-tapered diode lasers for medical treatment

“…The achieved modulation depth was 90%, and was limited by the longitudinal mode structure of the laser diode 12 . A higher modulation depth has been achieved for a similar system, but required heating the diode to 50°C 13 .…”