Low Loss Atomic Layer Deposited Al₂O₃ Waveguides for Applications in On-Chip Optical Amplifiers

Rare-earth ion doped Al2O3 for active integrated photonics

“…Al 2 O 3 can be deposited using a variety of methods including synthesis by the solgel method [52][53][54][55][56][57], chemical vapor deposition (CVD) [58,59], pulsed laser deposition (PLD) [60][61][62][63][64][65], atomic layer deposition (ALD) [11,27,[66][67][68][69][70][71][72][73] and reactive sputtering [3][4][5][6][7][8][9][10][12][13][14][15][16][20][21][22]26,[29][30][31][32][33][34][35][36][37][38]…”

“…Atomic layer deposition (ALD) is a chemical vapor deposition technique in which alternating gas precursors are flown over the substrate reacting with their surface in a self-terminating way, thereby growing a thin film [11,[68][69][70][71][72][73]. In between gases, a purging step is applied to eliminate any unreacted species before the start of the next cycle.…”

“…Nitrogen purging is usually reported for up to 8 sec per purge [66]. Deposition temperatures between 150 and 300 C have been investigated and the effect of the deposition temperature on the quality, i.e., refractive index and crystallinity, of the deposited layers has been reported [11]. The refractive index increased from 1.629 to 1.639 at a wavelength of 1550 nm for layers deposited at 150 C and 300 C, respectively.…”

“…Optical waveguiding has been shown in amorphous Al 2 O 3 at various wavelengths within its transparency window, including waveguides and devices at 371 nm [2], 1020 nm [3], 1550 nm [4][5][6][7] and 2000 nm [8]. Low optical losses down to 0.1 ± 0.02 dB/cm [9,10] and 0.04 ± 0.02 dB/cm in the C-band [11] have been demonstrated for planar slab waveguides deposited by reactive sputtering and atomic layer deposition, respectively. After waveguide definition with reactive ion etching, propagation losses below 0.2 dB/cm have been demonstrated at a wavelength of 1550 nm [6,9].…”

Single-layer active-passive Al2O3 photonic integration platform

“…Whereas Si and Si 3 N 4 have a low solubility for rare-earth ions [1,2], amorphous Al 2 O 3 can host high concentrations of those ions with moderate quenching of luminescence [3,4]. The ability to host high concentrations of rare-earth ions in combination with the wide transparency window (150-7000 nm) and low propagation loss [5,6], makes amorphous Al 2 O 3 an attractive material for UV, visible, nearand mid-IR on-chip active devices [7][8][9].…”