Reliable Low-Cost Fabrication of Low-Loss $\hbox{Al}_{2}\hbox{O} _{3}{:}\hbox{Er}^{3+}$ Waveguides With 5.4-dB Optical Gain

Abstract

A reliable and reproducible deposition process for the fabrication of Al 2 O 3 waveguides with losses as low as 0.1 dB/cm has been developed. The thin films are grown at 5 nm min deposition rate and exhibit excellent thickness uniformity within 1% over 50 50 mm 2 area and no detectable OH incorporation. For applications of the Al 2 O 3 films in compact, integrated optical devices, a high-quality channel waveguide fabrication process is utilized. Planar and channel propagation losses as low as 0.1 and 0.2 dB/cm, respectively, are demonstrated. For the development of active integrated optical functions, the implementation of rareearth-ion doping is investigated by cosputtering of erbium during the Al 2 O 3 layer growth. Dopant levels between 0.2-5 10 20 cm 3 are studied. At Er 3+ concentrations of interest for optical amplification, a lifetime of the 4 I 13 2 level as long as 7 ms is measured. Gain measurements over 6.4-cm propagation length in a 700-nm-thick Al 2 O 3 :Er 3+ channel waveguide result in net optical gain over a 41-nm-wide wavelength range between 1526-1567 nm with a maximum of 5.4 dB at 1533 nm.

High-gain Al2O3:Nd3+ channel waveguide amplifiers at 880 nm, 1060 nm, and 1330 nm

“…Deposition of planar Al 2 O 3 waveguides with and without rare-earth-ion dopants has been optimized by use of an AJA ATC 1500 reactive sputtering system equipped with RF sputtering guns, resulting in layers with low background loss [7]. Here, Al 2 O 3 :Nd 3+ layers with a thickness of 600 nm were reactively co-sputtered by the same system onto 8-µm thermally oxidized Si wafers.…”

“…Over the last two decades there has been significant interest in rare-earth-ion-doped planar waveguide amplifiers [1][2][3][4][5][6][7][8][9] for integrated optical applications. Such low-cost, compact components can be very useful for amplifying optical signals at a high data rate of 170 Gbit/s [8] and compensating optical losses owing to waveguide materials, signal routing, and input/output coupling within an integrated optical circuit.…”

“…Amorphous aluminium oxide (a-Al 2 O 3 ) has been investigated as a gain material due to its low loss, good mechanical stability and-compared to other amorphous dielectric materials-large thermal conductivity and refractive index, the latter property allowing high integration density [7]. Besides, Al 2 O 3 is compatible with Si-based technology.…”

Neodymium-doped waveguide amplifiers and lasers for integrated optical applications

“…Al 2 O 3 :Er 3+ waveguide amplifiers have been reported by several research groups [40][41][42][62][63][64][65][66]. A maximum internal net gain of 2 dB/cm at 1533 nm by pumping at 977 nm [40], and a net gain of up to 11 dB at 1532 nm with data transmission at a rate of 170 Gbit/s [42] …”

“…The deposition of Al 2 O 3 layer with Er dopants by reactive co-sputtering has been well developed in the IOMS group in previous work [41,42], and has been applied to the deposition of Al 2 O 3 :Nd 3+ films.…”