Er-doped light emitting slot waveguides monolithically integrated in a silicon photonic chip

Abstract

An integrated erbium-based light emitting diode has been realized in a waveguide configuration allowing 1.54 μm light signal routing in silicon photonic circuits. This injection device is based on an asymmetric horizontal slot waveguide where the active slot material is Er(3+) in SiO2 or Er(3+) in Si-rich oxide. The active horizontal slot waveguide allows optical confinement, guiding and lateral extraction of the light for on-chip distribution. Light is then coupled through a taper section to a passive Si waveguide terminated by a grating which extracts (or inserts) the light signal for measuring purposes. We measured an optical power density in the range of tens of μW/cm(2) which follows a super-linear dependence on injected current density. When the device is biased at high current density, upon a voltage pulse (pump signal), free-carrier and space charge absorption losses become large, attenuating a probe signal by more than 60 dB/cm and thus behaving conceptually as an electro-optical modulator. The integrated device reported here is the first example, still to be optimized, of a fundamental block to realize an integrated silicon photonic circuit with monolithic integration of the light emitter.

Electrical pump & probe and injected carrier losses quantification in Er doped Si slot waveguides

“…Finally, vias were etched down to the doped part of the waveguides and Al metal electrodes were formed (see ref. [11]). An optical mode confinement factor of 40% was calculated, defined as the ratio of the optical power in the slot and the total optical power [15].…”

“…[11] for further details). An infrared camera (Hamamatsu c2741) was used to monitor the guided mode at the output of the waveguide and ensure its good confinement.…”

“…To this end, several work investigated on the optical and electrical properties of slot waveguides, showing promising characteristics for their implementation as functional building blocks [8,9]. Active slot waveguides where light can be generated and simultaneously coupled to the rest of the photonic circuit were successfully designed [10] and fabricated [11] recently. Er 3+ doped Si-rich oxide (SRO) was used as a slot layer to yield good injection efficiency and high electroluminescence (EL) performance.…”

Compact focusing grating couplers for silicon horizontal slot waveguides

“…Multi-layer silicon PICs with material films deposition or direct wafer/ sample bonding yielding horizontal slot waveguides are promising solutions. Horizontal slot waveguides, where light confinement happens in a thin low refractive index layer sandwiched by thick high refractive index materials, allow for ultra-high optical confinement, light guiding, lateral extraction of light for on-chip distribution, light emitting devices, efficient nonlinear performance and, as mentioned above, multilayer functionalities allowing the combination of several optical layers or even of electronic and optical layers [2][3][4][5][6]. Among the materials involved in slot waveguides, amorphous silicon as a deposited material is a particularly promising approach for enabling the desired matching between on-chip optical layers, or even the integration with electronic ones, as it allows amorphous silicon to be deposited at a low temperature [by a well-suited CMOS-compatible plasma enhanced chemical vapor deposition (PECVD) process] which is an essential requirement in CMOS fabrication processes [7,8].…”

Infrared photoconductivity of Er-doped Si nanoclusters embedded in a slot waveguide

“…The fabrication details, slot waveguide design, and simulations could be found elsewhere. 14,15 Here, we provide only essential information for convenience. The slot waveguide is formed from multilayered silicon rich silicon oxide (SRO) embedded between 220 nm SOI and a 116-nm-thick polycrystalline silicon layers.…”