Applications of thin-film lithium niobate in nonlinear integrated photonics

Fig. 2. Crystal orientations and corresponding preferred polarization to achieve maximum efficiency for nonlinear processes in TFLN using [(a), (b)] quasi phase matching via periodic poling and [(c), (d)] modal phase matching.

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Fig. 3. Various phase-matching methods used on the TFLN platform. (a) Birefringent phase-matching.⁵⁹ (b) Modal phase matching.⁶⁰ (c) Grating-assisted quasi phase matching or mode shape modulation.⁶¹ (d) PPLN on a straight waveguide.¹³ (e) Natural quasi phase matching, which is conceptually similar to cyclic phase-matching.⁶² (f) Phase-matching-free metasurface.⁶³

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Fig. 4. PPLN devices in different structures. (a) Straight waveguide.⁸² (b) Racetrack resonator that is poled on one of the straight arms.⁸³ (c) Radially poled microring resonator.⁸⁴ (d) Radially poled microdisk, poled using the PFM technique in which they also demonstrated a poling period as small as 200 nm.⁸⁵

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Fig. 5. Some of the schemes used for implementing cascaded $χ^{(2)}$ processes in TFLN and the corresponding harmonic generations. (a) Two PPLN sections with different poling periods to enable SHG/SFG cascading for a THG device and SHG/SHG for an FHG device.¹³⁷ (b) Dual-period PPLN microdisk with demonstrated THG and FHG.⁹⁵ (c) THG and FHG on a single PPLN device via pulse pumping.⁸² (d) SHG and THG on a microdisk through cascaded SHG/SFG by taking advantage of the natural BPM.⁶⁹

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Fig. 6. Using second-order nonlinear processes for generating OFCs on lithium niobate. (a) Quadratic frequency comb generation on conventional LN¹⁴³ using cascaded $χ^{(2)}$ processes, which has yet to be demonstrated on the TFLN platform. (b) Electro-optic frequency comb generation in TFLN using coupled microring and racetrack resonators and the resulting spectrum exhibiting a high conversion efficiency.¹⁴⁸

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Fig. 7. SCG on the TFLN platform. (a) SCG spanning over two octaves in a dispersion engineered straight waveguide without poling.¹⁵⁹ (b) SCG on a periodically poled straight waveguide with a span of more than two octaves at a pulse energy of $\sim 11 pJ$ .¹³⁹ (c) Using cascaded SCG and SHG for on-chip $f - 2 f$ self-referencing, which is of great importance for realization of on-chip OFCs.¹⁵⁸

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Fig. 8. OFC generation in TFLN using the Kerr effect. (a) Conceptual schematic of a fully integrated soliton comb system in TFLN with all the required functionalities.¹⁶¹ (b) Soliton Kerr comb generation spanning near one octave.¹⁶² (c) Cascaded Kerr and EO combs with green lines corresponding to Kerr comb lines spanning over 200 nm.¹⁶³ (d) Zoomed in spectra of the cascaded Kerr and EO combs demonstrating that EO combs with much lower repetition rates fill the gap between Kerr combs.¹⁶³

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Table 1. Optical properties of some of the materials used for second-order nonlinear applications.
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Table 1. Optical properties of some of the materials used for second-order nonlinear applications.
Material Largest $d$ coefficient Refractive index at 1550 nm
${LiNbO}_{3}$ ⁵¹ $d_{33} = 27 pm / V$ $\sim 2.2$
AlN⁵² $d_{33} = 4.7 pm / V$ $\sim 2.1$
GaAs⁵¹ $d_{36} = 119 pm / V$ $\sim 3.4$
GaN⁵³ $d_{33} = 16.5 pm / V$ $\sim 2.3$

Table 2. Performance of various devices based on straight waveguide structure for SHG using different phase-matching methods. Power values for the pump and SH wavelength and the absolute conversion efficiency (in %) correspond to the maximum normalized conversion efficiency and are not necessarily the maximum reported numbers in these papers.

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Table 2. Performance of various devices based on straight waveguide structure for SHG using different phase-matching methods. Power values for the pump and SH wavelength and the absolute conversion efficiency (in %) correspond to the maximum normalized conversion efficiency and are not necessarily the maximum reported numbers in these papers.


PM method	Pump/SH power	Length	$% W^{- 1} {cm}^{- 2}$	$% W^{- 1}$	Absolute %
BPM type-I⁵⁹	$25 mW / 67 μ W$	2 cm	2.7	10.7	$\sim 0.27$
MPM type-0⁶⁷	$630 μ W / 140 nW$	2.35 mm	650	36	$\sim 0.022$
PPLN type-0⁸²	$3 mW / 370 nW$	$300 μ m$	4600	4.14	$\sim 0.012$
PPLN type-0⁸⁸	$530 μ W / 2.7 μ W$	5 mm	3757	939.25	$\sim 0.5$
PPLN type-0⁸⁶	$1.5 mW / 9.4 μ W$	4 mm	2600	416	$\sim 0.6$
PPLN type-0⁸⁷	$2.95 mW / 31.6 μ W$	4 mm	2200	352	$\sim 1$
PPLN type-0⁸⁹	$\sim 6 mW / 550 μ W$	20 mm	$\sim 320$	$\sim 1280$	$\sim 9$

Table 3. Comparison of resonant-based structures for SHG using different phase-matching methods.

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Table 3. Comparison of resonant-based structures for SHG using different phase-matching methods.


Structure	PM method	Pump/SH power	$Q_{L}$ at FW	$% W^{- 1}$	Absolute %
Microring⁶⁰	MPM type-0	$440 μ W / 2.9 μ W$	$1.4 \times 10^{5}$	1500	$\sim 0.65$
Microring⁸⁴	PPLN type-0	$1.05 μ W / 56 nW$	$1.8 \times 10^{6}$	$5 \times 10^{6}$	$\sim 5.3$
Microring⁹⁰	PPLN type-I	$55 μ W / 7.5 μ W$	$8 \times 10^{5}$	$2.5 \times 10^{5}$	$\sim 13.5$
Racetrack⁸³	PPLN type-0	$5.6 μ W / 73 nW$	$3.7 \times 10^{5}$	$2.3 \times 10^{5}$	$\sim 1.3$
Microdisk⁹¹	CPM type-I	$10 mW / 110 μ W$	$1.1 \times 10^{5}$	$\sim 110$	$\sim 1.1$
Microdisk¹⁶	NQPM type-0	$30 μ W / 4.2 μ W$	$7.5 \times 10^{7}$	$4.7 \times 10^{5}$	$\sim 14$

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Milad Gholipour Vazimali, Sasan Fathpour, "Applications of thin-film lithium niobate in nonlinear integrated photonics," Adv. Photon. 4, 034001 (2022)

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Paper Information

Category: Reviews

Received: Mar. 15, 2022

Accepted: May. 3, 2022

Posted: May. 6, 2022

Published Online: Jun. 2, 2022

The Author Email: Fathpour Sasan (fathpour@creol.ucf.edu)

DOI:10.1117/1.AP.4.3.034001

Topics

laser devices and laser physics

Lasers and Laser Optics

Laser physics

laser manufacturing

Instrumentation, Measurement and Metrology

Table 1. Optical properties of some of the materials used for second-order nonlinear applications.

Table 1. Optical properties of some of the materials used for second-order nonlinear applications.

Table 3. Comparison of resonant-based structures for SHG using different phase-matching methods.

Table 3. Comparison of resonant-based structures for SHG using different phase-matching methods.