Optical parametric amplifiers
It has been known considering that the 80s that the intrinsic nonlinearity of fiber optics can also be utilized to create traveling-wave optical parametric amplifiers, whose gain is independent of atomic or semiconductor transitions, which indicates that it can be broad-band and practically cover any wavelength.
Parametric amplifiers also do not struggle with a minimum input signal, which implies that they can be utilized to enhance both the faintest signals and big input power in a single setting. The gain spectrum can be customized by waveguide geometry optimization and dispersion engineering, which offers enormous design flexibility for target wavelengths and applications.
Many intriguingly, parametric gain can be obtained in unusual wavelength bands that are out of reach of rare-earth-doped fibers or standard semiconductors. Parametric amplification is naturally quantum-limited, and can even achieve soundless amplification.
Silicon constraints
Regardless of their attractive functions, optical parametric amplifiers in fibers are intensified by their extremely high pump power requirements arising from the weak Kerr nonlinearity of silica. Over the previous 20 years, the advances in integrated photonic platforms have allowed considerably improved efficient Kerr nonlinearity that can not be accomplished in silica fibers but has actually not accomplished continuous-wave-operated amplifiers.
” Operating in the continuous-wave routine is not a simple academic accomplishment,” says Professor Tobias Kippenberg, head of EPFLs Laboratory of Photonics and Quantum Measurements at EPFL. “In fact, it is important to the practical operation of any amplifier, as it implies that any input signals can be magnified– for instance, optically encoded info, signals from LiDAR, sensing units, and so on. Time- and spectrum-continuous, traveling-wave amplification is essential for effective implementation of amplifier innovations in contemporary optical interaction systems and emerging applications for optical noticing and varying.”
Breakthrough photonic chip
A new research study led by Dr. Johann Riemensberger in Kippenbergs group has actually now dealt with the difficulty by developing a traveling-wave amplifier based upon a photonic integrated circuit operating in the constant routine. “Our results are a culmination of more than a decade of research study effort in incorporated nonlinear photonics and the pursuit of ever lower waveguide losses,” says Riemensberger.
The researchers used an ultralow-loss silicon nitride photonic integrated circuit more than two meters long to construct the very first traveling-wave amplifier on a photonic chip 3 × 5 mm2 in size. The chip runs in a continuous regime and supplies 7 dB net gain on-chip and 2 dB net gain fiber-to-fiber in the telecommunication bands. On-chip net-gain parametric amplification in silicon nitride was also just recently attained by the groups of Victor Torres-Company and Peter Andrekson at Chalmers University.
In the future, the team can utilize accurate lithographic control to optimize the waveguide dispersion for parametric gain bandwidth of more than 200 nm. And because the essential absorption loss of silicon nitride is extremely low (around 0.15 dB/meter), additional fabrication optimizations can press the chips optimum parametric gain beyond 70 dB with only 750 mW of pump power, exceeding the performance of the very best fiber-based amplifiers.
” The application locations of such amplifiers are limitless,” says Kippenberg. “From optical communications where one could extend signals beyond the common telecommunication bands, to mid-infrared or visible laser and signal amplification, to LiDAR or other applications where lasers are utilized to probe, sense and question classical or quantum signals.”
Reference: “A photonic integrated continuous-travelling-wave parametric amplifier” by Johann Riemensberger, Nikolai Kuznetsov, Junqiu Liu, Jijun He, Rui Ning Wang and Tobias J. Kippenberg, 30 November 2022, Nature.DOI: 10.1038/ s41586-022-05329-1.
The photonic integrated circuits utilized in this research study. Credit: Tobias Kippenberg (EPFL), CC BY 4.0
The ability to magnify optical signals in optical fibers to their quantum limit is an important technological improvement that underpins our modern details society. The 1550 nm wavelength band is utilized in optical telecommunications because it not just has low loss in silica fiber optics (for which the 2008 Nobel Prize in Physics was awarded), however also since it permits for the amplification of these signals, essential for trans-oceanic fiber optical interaction.
Optical amplification plays an essential role in practically all laser-based technologies such as optical communication, utilized for example in information centers to interact between servers and between continents through trans-oceanic fiber links, to ranging applications like coherent Frequency Modulated Continuous Wave (FMCW) LiDAR– an emerging technology that can spot and track items farther, much faster, and with higher precision than ever in the past. Today, optical amplifiers based on rare-earth ions like erbium, in addition to III-V semiconductors, are widely utilized in real-world applications.
These two methods are based on amplification by optical transitions. However there is another paradigm of optical signal amplification: traveling-wave parametric amplifiers, which accomplish signal amplification by differing a little system “parameter”, such as the capacitance or the nonlinearity of a transmission line.
“In truth, it is crucial to the useful operation of any amplifier, as it implies that any input signals can be amplified– for example, optically encoded information, signals from LiDAR, sensors, etc. Time- and spectrum-continuous, traveling-wave amplification is critical for effective application of amplifier technologies in contemporary optical communication systems and emerging applications for optical ranging and noticing.”
The scientists utilized an ultralow-loss silicon nitride photonic incorporated circuit more than two meters long to construct the first traveling-wave amplifier on a photonic chip 3 × 5 mm2 in size. The chip operates in a continuous program and supplies 7 dB net gain on-chip and 2 dB net gain fiber-to-fiber in the telecommunication bands. On-chip net-gain parametric amplification in silicon nitride was likewise just recently attained by the groups of Victor Torres-Company and Peter Andrekson at Chalmers University.