We demonstrate a fully packaged hybrid integrated laser and a soliton microcomb with frequency actuation bandwidth of more than 10 MHz and ultra-low laser frequency noise. The flat frequency response in the range of >1 MHz and the optical laser frequency chirp range of >1 GHz are compatible with high-resolution continuous wave frequency modulated distance ranging and distributed fiber optic sensing without any linearization or pre-distortion. The features of a novel laser system assembled in 14-pin butterfly package are enabled by the ultra-low loss silicon nitride platform and monolithically integrated piezo-electric actuators.
We developed original model describing the process of frequency comb generation in the self-injection locking regime and performed numerical modelling of this process. Generation of dissipative Kerr solitons in the self-injection locking regime at anomalous GVD was observed and studied numerically. It was proposed that self-injection locking may provide easy way for generation of frequency comb at normal group velocity dispersion. This idea was investigated in detail and platicon generation was demonstrated. Parameter range providing platicon excitation was found.
The ultra-narrow linewidth diode lasers self-injection locked to high-Q crystalline microresonators are available commercially, providing the linewidth below 1 kHz for various wavelengths and enabling microcomb generation. Here we demonstrate a technique that allows applying this approach for photonic integrated chips containing microresonators and significantly narrow the laser diode (Fabry-Perot or DFB) linewidth due to self-injection locking to the silicon nitride (SiN) microresonator with high Q-factor. Considered laser diodes are CMOS-compatible, as well as integrated microresonators made of silicon nitride. This makes it possible to realize in the future large-scale production of laser devices based on microresonators.
We stabilized the InGaAsP/InP Fabry-Perot (FP) laser diode (Seminex, 100 mW, 1535 nm, 20 nm spectral width) and the DFB laser (Nolatech Company, 1550 nm, output power up to 20 mW) by different silicon nitride microresonators with Q-factor higher than one million (LIGENTECH Company). Microresonators with different free spectral ranges (1 THz, 150 GHz, 35 GHz) allowed observing the different regime of operation, single frequency, and multi-frequency, when different laser diode lines are suppressed. The spectral linewidth of each locked line was better than 20 kHz (limited by Ref. laser).
The developed technique allowed us to integrate different types of laser diodes with high-Q SiN microresonators and developed a fully integrated optical frequency comb source. We measured spectral characteristics (spectral linewidth, phase noises) of free running and locked states, the stabilization coefficient, and the locking range and compare these values to the theoretical estimations. We discuss requirements for the optical frequency comb generation in such systems and demonstrate measured spectra of optical combs. Also, we discuss possible applications of such system, operating in multi-frequency locking or comb regimes, and demonstrate the application for spectroscopy measurements.
Optical frequency combs (OFC's) are extremely important for optoelectronics to date. They have found a great variety of practical applications. Some of proposed OFCs generation methods apply acousto-optic (AO) devices. The AO devices in such schemes are used either as the element devoted to the OFC phase stabilization or, much less often, they play the role of the key element responsible for optical radiation frequency shifting in the frequency-shifting loop (FSL). In this paper we continue the theoretical examination of new OFC generation method based on joint application of collinear AO diffraction geometry and FSL. This method gives two novel OFC generation schemes. In the first one collinear AO cell is fed by radio-frequency (RF) generator and FSL connects AO cell optical output and input. The second scheme includes not only FSL but also the optoelectronic feedback connecting the optical output of the system with the piezoelectric transducer of the AO cell. In this case the system operates like optoelectronic generator and external RF generator is not needed. The theoretical model is presented for both cases. Each of the systems gives the possibility to generate OFCs in several ways with varying characteristics. The influence of collinear AO diffraction parameters on the generated OFC characteristics such as spectral width, number of spectral components and envelope shape is examined.
Optical frequency combs (OFC) occupy an important place in modern optoelectronics. Plenty of OFC generation methods and practical application concepts were proposed in recent decade. Among the generation methods are several based on acousto-optic (AO) interaction application. In this paper we theoretically examine new OFC generation method based on joint use of collinear AO diffraction and frequency-shifting loop. This method gives two novel OFC generation schemes. The first one contains collinear AO cell driven by radio-frequency (RF) generator and optical loop connecting optical output and input of the AO cell. The second one includes not only the optical loop but also the optoelectronic feedback connecting the optical output of the system with the piezoelectric transducer of the AO cell. In this case the system operates above the self-excitation threshold without RF generator. Both systems were examined theoretically, it was discovered that they give the possibility to generate OFC’s in several ways. The switching between them is realized by mutual reorientation of a pair of polarizers placed before and behind the AO cell and achromatic half-wave plate included in the optical feedback loop. It is shown that the parameters OFCs obtained in the system with only optical feedback are determined by AO cell material, RF generator signal frequency and magnitude, optical loss and amplification. The system with both optic and electronic feedback gives the unique opportunity to obtain chirped OFCs.
We introduce a technique capable to produce and control stabilized single-frequency emission with a sub-kHz linewidth and independently soliton comb generation from a multi–frequency regular Fabry-Perot laser diode selfinjection locked to a high-Q optical microresonator. We also observed novel regimes of controllable single, dual, and multiple-frequency generation that may be useful for the creation of narrow-linewidth lasers required for the spectroscopy, LIDARs, and telecommunications. For analysis of the considered effects original theoretical models taking into account self-injection locking effect, mode competition and Bogatov asymmetric mode interaction were developed and numerical modeling was performed.
Silicon is a widely used material in modern microelectronics and photonics. Extremely low optical losses in near and mid-IR wavelengths made it a promising material for whispering gallery mode (WGM) optical micro-resonators. But, till now its potential was not fully utilized because of the best-obtained quality factor - about 2 x 107 - remained orders of magnitude below the material absorption limit. In this work we experimentally demonstrated a quality factor above 109 for the WGM in millimetres size crystalline silicon resonators. Materials with different residual conductivity were compared. Application of original semi-spherical silicon coupler allowed to obtain up to 35% resonance peaks contrast.
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