On-chip electrically reconfigurable octave-bandwidth optical amplification from visible to near-infrared

Abstract

Achieving broadband on-chip optical amplification spanning the visible and near-infrared (NIR) can enable diverse quantum sensing, metrology, and classical communication applications within a single unified device. However, conventional semiconductor and ion-doped amplifiers suffer from limited gain bandwidths set by fixed energy levels, while optical parametric amplifiers (OPAs) operating continuously from the visible to the NIR have remained elusive due to dispersion-limited bandwidth and the high pump powers required in the visible or ultraviolet (UV). Here, we overcome these limitations by introducing an electrically reconfigurable OPA architecture on lithium niobate integrated photonics. By synergistically combining ultra-high effective $χ^{(2)}$ nonlinearity ($\sim$7,000\%/W-cm$^2$), high-order dispersion engineering, and local electro-thermal tuning of quasi-phase matching, our device achieves record gain spectral spanning more than an optical octave, from 770 to 1650 nm. This range covers key transitions of many photonic quantum systems and all telecommunication bands. Moreover, our approach eliminates the need for high-power, wavelength-tunable visible or UV pumps, delivering a peak on-chip gain of 23.67 dB with a single 1060 nm pump at 90 mW average on-chip power. This work opens new avenues for multi-functional, reconfigurable photonics unifying the visible and infrared regimes, with broad implications for quantum sensing and communications.

Figures (5)

• Figure 1: Concept and design of integrated electrically reconfigurable vis-to-NIR OPA.a, Schematic and operating principle of the electrically reconfigurable vis-to-NIR OPA. b, Calculated 3 dB parametric gain bandwidth versus $\eta_0$ and $\beta_4$ when $\beta_2=0$. c, Optimized waveguide cross-sectional geometry and fundamental TE mode profiles of FH (1064 nm, left) and SH (532 nm, right) inside the waveguide. d, Calculated $\beta_2$ (blue) and $\beta_4$ (red) of the waveguide with optimized cross-sectional geometry, showing a near-zero $\beta_2$ of -3.6 fs$^2$/mm and a low $\beta_4$ of 543 fs$^4$/mm at the FH wavelength. e, Ultra-broadband gain coverage and phase matching characteristics under electro-thermal tuning. At $\Delta T=0$, co-optimization of near-zero $\beta_2$ and $\beta_4$ contributes to a significantly flattened phase mismatch (lower panel) and near-octave gain spectrum near degeneracy (middle panel). Electro-thermal tuning ($\Delta T>0$) further extends the gain spectral overage to 720-1900 nm, supporting various quantum and classical applications across NIR and visible spectrum (upper panel).
• Figure 2: Integrated electrically reconfigurable vis-to-NIR OPA and its basic $\chi^{(2)}$ nonlinear characteristics. a, Optical microscope image of the OPA, which consists of a 2-mm-long SHG section followed by a 5-mm-long tunable OPA section. b, Two-photon microscopy of the periodic poling before waveguide fabrication, revealing a poling period of 2.55 $\mu$m with a duty cycle of $\sim$50%. c, 45$^{\circ}$ titled false color SEM image of the nanophotonic TFLN waveguides and neighboring NiCr microheaters (yellow). Two waveguides were fabricated within one poling region. d, Measured on-chip SH power (blue symbols) as a function of FH power and its parabolic fit (red solid line), showing an ultra-high $\eta_0$ of 6898 %/W-cm$^2$. Inset: Measured (blue) and theoretical (red) SHG power as a function of the input FH wavelength. e, Upper panel: At room temperature, increased pump power induces a strong photorefractive blue-shift of the phase-matching wavelength. Lower panel: Elevating the chip temperature ($T_0$) to 70 °C yields a power-independent, stable phase-matching wavelength.
• Figure 3: Characterization of OPA at degeneracy ($V_\mathrm{DC}=0$).a, Experimental setup for OPA measurements. The OPA chip is mounted on a TEC stablized at $T_0=70^\circ\mathrm{C}$. A programmble DC bias is applied for thermo-optic tuning. CTL: continuous tunable laser; YDFA: ytterbium-doped fiber amplifier; TEC: thermoelectric cooler; OSA: optical spectrum analyzer; OSC: oscilloscope; PC: polarization controller; PD: photodetector. b, Upper panel: microscope image of the OPA showing the spatial evolution of the on-chip generated (green light) SHG power. Lower panel: Simulated on-chip FH (red) and SH (green) power evolution for an on-chip average pump power of 70 mW. c, Measured on-chip SH and FH output powers (symbols) versus on-chip input FH average power, compared with simulation (solid lines). d, Upper panel: measured parametric gain (symbols) for on-chip pump powers of 50, 70, and 90 mW (with $V_\mathrm{DC}=0$), overlaid with the corresponding spontaneous parametric fluorescence (solid lines). Inset: measured peak gain (blue symbols) at 920 nm as a function of on-chip pump power, showing good agreement between experiment and simulation (red solid line). Lower panel: measured (symbol) and calculated (solid line) wavelength-dependent noise figure (NF) (symbols) with 90 mW on-chip FH average power.
• Figure 4: Electrically reconfigurable visible-to-NIR OPA.a, Electrically reconfigurable parametric gain across visible and NIR bands at different V$_\mathrm{DC}$. Upon applying V$_\mathrm{DC}$, the OPA switches to the nondegenerate regime and the gain spectral coverage is further extended to more than one octave, from 770 nm to 1650 nm. Shaded areas highlight telecommunication bands and important spectral regions for photonic quantum technologies. QD: quantum dot; hBN: hexagonal boron nitride; SPE: single-photon emitter; PSB: photon sideband. b, output optical spectra measured without (orange) and with (blue) 90 mW on-chip average power at 1060 nm when an 2 mW (off-chip power) 1550 nm coherent signal was injected. Inset: Zoomed-in optical spectra. The span of the OSA is 4 nm with a 0.05 nm resolution. c, Upper panel: on-chip signal output power at wavelength 1550 nm as a function of signal powers at the input of the OPA, showing an unsaturated on/off gain of 18.1 dB at a 90 mW on-chip pump power. Lower panel: measured NF as a function of on-chip signal power.
• Figure 5: Comparison of operational bandwidth of various optical amplifier technologies.