Stimulated emission in the active planar optical waveguide made of silicon nanocrystals

Abstract

Thin layers of silicon nanocrystals prepared by silicon-ion implantation into silica substrate form active planar optical waveguides. Testing experiments of optical gain have been performed on a sample implanted to a dose of 4×10 17 cm -2 by using the variable stripe length (VSL) technique. The photoluminescence collected from the sample facet shows spectrally narrow, polarization-resolved transverse electric (TE) and transverse magnetic (TM) substrate modes. Continuous wave VSL revealed a reduction of optical losses in both modes only. On the contrary, a fast decay component due to amplified spontaneous emission is observed in time-resolved VSL experiments. This fast component shows positive net modal optical gain of ~12 cm -1. The observed superlinear emission as a function of pump intensity, accompanied by shortening of the fast component lifetime, supports further the observation of stimulated emission.

Silicon quantum dots: surface matters

“…Low optical gain in SiQD systems is typically investigated using the variable stripe length (VSL) technique [399,400]. The most commonly occurring 'false gain' artifacts are waveguiding effects [401,402], interference on the VSL slit [9] and generally also the non-constant light out-coupling into the detection system [403]. Most of these effects can be eliminated by the use of the shifting excitation spot technique [403], developed during the studies of gain in SiQDs and tested on porSi O : SiQDs [12,398,401,402] and Er-doped SiQDs in silica [338].…”

“…The most commonly occurring 'false gain' artifacts are waveguiding effects [401,402], interference on the VSL slit [9] and generally also the non-constant light out-coupling into the detection system [403]. Most of these effects can be eliminated by the use of the shifting excitation spot technique [403], developed during the studies of gain in SiQDs and tested on porSi O : SiQDs [12,398,401,402] and Er-doped SiQDs in silica [338]. Besides the experimental challenges, the main obstacles in various SiQD systems are [20] (i) free carrier losses, (ii) the lack of a four-level system, (iii) broad size-distribution or (iv) scattering of the emitted light.…”

Stimulated emission at 1.54 μm from erbium/oxygen-doped silicon-based light-emitting diodes

“…Moreover, a super-linearly growing electroluminescence (EL) is obtained with a slope efficiency beyond 2 even at room temperature. The low threshold of ~6 mA (~0.8 A/cm 2 ) [19,20], the super-linear EL integral intensity [21][22][23], the narrowing full width at half maximum (FWHM) [24,25], and the Gaussian-like spatial emission distribution [26,27], as well as the fast radiation recombination lifetime [28][29][30][31], confirm the presence of stimulated emission involving transitions related to the Er 3+ [32][33][34]. Time-resolved PL (TR-PL) and photocurrent (PC) measurements reveal the relaxation dynamics of the nonequilibrium carriers from the Si host to the Er 3+ precipitates.…”

Silicon nanocrystals in silica—Novel active waveguides for nanophotonics

“…On the other hand the propagation path of radiative modes through a pumped active medium (Si-NCs forming the waveguide) is limited by leakage into the substrate. Attempts to achieve optical gain on leaking modes was successful only under strong nanosecond pulsed pumping (6 ns, 355 nm from THGNd:YAG laser) with the gain threshold around 50 mJ/cm 2 and maximum gain at TM mode of about 12 cm À1 for 100 mJ/cm 2 excitation [21].…”