Optically pumped planar waveguide lasers, Part I: Fundamentals and fabrication techniques

Abstract

Abstract:The tremendous interest in the field of waveguide lasers in the past two decades is largely attributed to the geometry of the gain medium, which provides the possibility to store optical energy on a very small dimension in the form of an optical mode. This allows for realization of sources with enhanced optical gain, low lasing threshold, and small footprint and opens up exciting possibilities in the area of integrated optics by facilitating their on-chip integration with different functionalities and highly compact photonic circuits. Moreover, this geometrical concept is compatible with high power diode pumping schemes as it provides exceptional thermal management, minimizing the impact of thermal loading on laser performance. The proliferation of techniques for fabrication and processing capable of producing high optical quality waveguides has greatly contributed to the growth of waveguide lasers from a topic of fundamental research to an area that encompasses a variety of practical applications. In this first part of the review on optically pumped waveguide lasers the properties that distinguish these sources from other classes of lasers will be discussed. Furthermore, the current state-of-the art in terms of fabrication tools used for producing waveguide lasers is reviewed from the aspects of the processes and the materials involved. 2 1.IntroductionOver the last two decades the field of solid-state planar waveguide lasers has experienced a steady growth, progressing from a laboratory curiosity to an area that demonstrates a broad spectrum of applications, from multiwavelength laser channel arrays for telecommunications to diode-pumped planar structures with multiwatt output powers for sensing and ranging applications. Waveguide lasers are by no means a new field and the first report on such a source dates back in 1961, when laser operation of a waveguide based on an active glass core rod embedded in a low refractive index cladding was demonstrated [1]. However research efforts in the years that followed this report focused primarily on the development of optically pumped laser sources based on high optical quality bulk dielectric laser media in the form of rods and slabs. The merits of the waveguide geometry and the associated optical confinement have been first highlighted in single mode glass optical fibers. Fibers have proven an enabling technology for realization of highly efficient amplifier and laser sources owing to their unrivalled low loss performance and ability to maintain a small spot size and hence high intensities over lengths that are orders of magnitude longer than would normally be allowed by diffraction, [2,3]. Er-doped fiber amplifiers (EDFAs) in particular have directly contributed to the enormous expansion of the optical communications networks that underpin today's internet infrastructure by allowing for signal regeneration and optical data transmission over long distances. The excellent performance of fiber lasers and amplifiers provided motivation and triggered a major techn...

Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

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15 GHz picosecond pulse generation from a monolithic waveguide laser with a graphene-film saturable output coupler

“…We get mode-locked pulses with 1.5GHz repetition rate and 202mW average output power, with a 48% slope efficiency (i.e. rate of output to pump power in excess of the lasing threshold 28 ) and 38% optical-to-optical conversion efficiency (i.e. rate of output to pump power 28 ).…”

“…rate of output to pump power in excess of the lasing threshold 28 ) and 38% optical-to-optical conversion efficiency (i.e. rate of output to pump power 28 ). The slope efficiency is high compared with that typical of monolithic pulsed waveguide lasers (e.g.…”

Holmium-doped 21 μm waveguide chip laser with an output power > 1 W

“…In the last two decades, waveguides structures in bulk materials have emerged as a complementary combination of solid-state bulk lasers and fiber lasers [7], trading average power to achieve compact geometries [8,9]. Like solid-state lasers, they can reach considerable levels of energy storage in a small active volume.…”