Multi-stage optical amplifier having photonic-crystal waveguides for generation of high-power pulsed radiation and associated method

An apparatus comprising:

• an optical amplifier having a segmented fiber that includes a first amplifying segment having a rare-earth-doped photonic-crystal core and a second amplifying segment having a rare-earth-doped photonic-crystal core, wherein the first segment amplifies to a higher power than the second segment and is non-contiguous with the second segment;
• a master-oscillator subsystem operable to obtain a seed laser signal light and to optically couple the seed laser signal light into the second segment, and
• a first optical-connector subassembly operatively coupled between the second segment and the first segment, wherein the first optical-connector subassembly includes:
• an enclosure having a substrate;
• an optical band-pass filter attached to the substrate;
• a dichroic mirror/beamsplitter, attached to the substrate, that directs pump light into the second segment in a counter-propagating direction relative to signal light, and directs signal light from the second segment to the first segment through the optical band-pass filter;
• and
• at least one lens attached to the substrate;
• wherein at least one of the filter, the mirror/beamsplitter and the lens is soldered to the enclosure to form a unitized assembly.

An apparatus comprising:

• an optical amplifier that includes:
• first photonic-crystal means for amplifying optical signal pulses to obtain high-power optical signal pulses, second photonic-crystal means for amplifying optical signal pulses to obtain intermediate-power optical signal pulses, wherein the second means is non-contiguous with the first means, and means for optically coupling the intermediate-power optical signal pulses to the first amplifying means from the second amplifying means;
• and
• means for generating optical seed signal pulses and for coupling the optical seed signal pulses into the second amplifying means.

A method comprising:

• providing an optical amplifier having a segmented photonic-crystal fiber that includes a higher-power first amplifying segment having a rare-earth-doped photonic-crystal core and a lower-power second amplifying segment having a rare-earth-doped photonic-crystal core;
• obtaining a seed laser signal;
• optically coupling the seed laser signal into the core of the second amplifying segment;
• amplifying the seed laser signal in the second amplifying segment to obtain intermediate-power signal light;
• operatively coupling the intermediate-power signal light to the first amplifying segment from the second amplifying segment;
• and
• amplifying the intermediate-power signal light in the first amplifying segment to obtain higher-power signal light.