Single mode fiber coupled tapered laser module with frequency stabilized spectrum

Abstract

Laser modules for single mode fiber (SMF) coupling of frequency stabilized diode lasers are so far mainly realized with ridge lasers due to their good beam quality. Tapered lasers are beam sources with a beam quality which is nearly as good as that of a ridge laser but with a higher optical output power. Therefore they have the potential for a higher SMF-coupled power than ridge lasers. It will be shown how the radiation of a tapered laser or amplifier can be frequency stabilized and coupled into a SMF in a compactly build module. To couple a tapered laser different coupling systems, using cylindrical lenses either crossed or in combination with rotational lenses are possible. The advantages, problems and coupling results of those systems will be illustrated. For many applications it is necessary to stabilize the frequency of the laser. This can be achieved for example by a fiber bragg grating, written in the SMF in which the laser is coupled or by a volume holographic grating, applied to a lens in the coupling system. Another possibility is the use of a tapered amplifier, which is stabilized by a fiber bragg grating on the backside of the amplifier

FDML swept source at 1060 nm using a tapered amplifier

“…Furthermore, optimizing the feedback to the tapered amplifier will increase the achievable output power, and it can be expected that this will also lead to lower intensity noise and higher sensitivity. The integration of a tapered amplifier into a fiber-pigtailed package has been demonstrated, 11 thus the fiber-coupling can be compact and stable, with minimized losses. All this opens the possibility for high-speed swept source applications at 1060 nm with increased power requirements, such as buffered FDML or imaging with multiple beams.…”

Opto-Electronics Review

“…Various designs of TA modules have been proposed, e.g., [68,[73][74][75][76][77]97]. Our design is inspired by Ref.…”

“…In brief, the incoming beam is set to be collinear with the amplified spontaneous emission (ASE) emitted from the rear facet of the unseeded TA. For an ideal coupling efficiency, the waist of the collimated seed beam should lie in the entrance facet of the TA waveguide, while its diameter and the divergence angle should coincide with the values for the backward emitted beam [97].…”

Fourier domain mode-locked swept source at 1050 nm based on a tapered amplifier

“…In a simple freespace cw-resonator, our tapered amplifier emitted several hundred milliwatts with 1 to 2 A drive current, and in general such devices can generate several watts of laser light [21,28]. Apparently, the feedback in the current fiber-optic configuration is not sufficient to saturate the gain of the tapered amplifier.…”

“…One could, for example, use an SOA with higher saturation power or optimize the fiber-coupling. The integration of a tapered amplifier into a fiber-pigtailed package, as demonstrated by Haverkamp et al [28], could make the setup very stable and compact. As confirmed by preliminary tests, higher output power is also possible by increasing the tapered amplifier drive current.…”