Er:fiber-based femtosecond frequency comb stabilized to an Yb+ single-ion optical frequency standard

An erbium fiber-based femtosecond optical frequency comb stabilized to an Yb+ single-ion optical frequency standard was created. For the first time, a combination of an extra-cavity acousto-optic frequency modulator with fiber outputs and an intracavity electro-optic phase modulator based on a KTP crystal were used to stabilize offset frequency and one of the optical components of the Er:fiber femtosecond comb. As a result a locking bandwidth of 30 kHz for the optical comb offset frequency has been obtained. It is shown that the relative instability introduced by the stabilization and measurement systems into the output radio frequencies (in addition to the instability of the reference optical signal) is no worse than 5 × 10−14 for averaging times of 1 s and 2 × 10−16 for averaging times of 400 s.

Aluminum nitride nanophotonics for beyond-octave soliton microcomb generation and self-referencing

Frequency microcombs, alternative to mode-locked laser and fiber combs, enable miniature rulers of light for applications including precision metrology, molecular fingerprinting and exoplanet discoveries. To enable frequency ruling functions, microcombs must be stabilized by locking their carrier-envelope offset frequency. So far, the microcomb stabilization remains compounded by the elaborate optics external to the chip, thus evading its scaling benefit. To address this challenge, here we demonstrate a nanophotonic chip solution based on aluminum nitride thin films, which simultaneously offer optical Kerr nonlinearity for generating octave soliton combs and quadratic nonlinearity for enabling heterodyne detection of the offset frequency. The agile dispersion control of crystalline aluminum nitride photonics permits high-fidelity generation of solitons with features including 1.5-octave spectral span, dual dispersive waves, and sub-terahertz repetition rates down to 220 gigahertz. These attractive characteristics, aided by on-chip phase-matched aluminum nitride waveguides, allow the full determination of the offset frequency. Our proof-of-principle demonstration represents an important milestone towards fully integrated self-locked microcombs for portable optical atomic clocks and frequency synthesizers.

CMOS RF Front-Ends For Bluetooth Applications

This project investigates the design of RF front-ends for bluetooth applications. The main objectives in each design are optimized noise figure, power consumption, gain and linearity. The designed cascode LNA achieves 1.37 dB low noise figure through ports matching and maximizes the voltage gain to 11.5 dB. The port isolation reaches to 82 dB. A 2 MHz low IF down-conversion mixer is developed. It employs current injection to reduce the flicker noise of MOSFETs. The total noise figure of the mixer is 17 dB and input referred IIP3 is 4.97 dB. A quadrature mixer constructed by two symmetric Gilbert mixers are discussed. A common-gate class E power amplifier is investigated. Through connecting a L matching network, the output power would be 17.7 dBm at 1.4 V power supply and the power added efficiency PAE and drain efficiency DE are 41% and 42.8 % respectively. To supply two LO frequencies with 90º phase difference, a quadrature voltage controlled oscillator is designed using a series of coupling structure and accumulation mode PMOS varactors. The frequency tuning range is 2.304 GHz ~ 2.54 GHz when the control voltage changes from 0 to 0.7 V. The QVCO exhibits phase noise of -113 dBc/Hz at 600 kHz offset frequency and -119 dBc.Hz at 1 MHz offset frequency. All the circuits were designed in TSMC-0.18μm 1.8 V CMOS technology and simulated using HSPICE RF simulator.

CMOS RF Front-Ends For Bluetooth Applications

This project investigates the design of RF front-ends for bluetooth applications. The main objectives in each design are optimized noise figure, power consumption, gain and linearity. The designed cascode LNA achieves 1.37 dB low noise figure through ports matching and maximizes the voltage gain to 11.5 dB. The port isolation reaches to 82 dB. A 2 MHz low IF down-conversion mixer is developed. It employs current injection to reduce the flicker noise of MOSFETs. The total noise figure of the mixer is 17 dB and input referred IIP3 is 4.97 dB. A quadrature mixer constructed by two symmetric Gilbert mixers are discussed. A common-gate class E power amplifier is investigated. Through connecting a L matching network, the output power would be 17.7 dBm at 1.4 V power supply and the power added efficiency PAE and drain efficiency DE are 41% and 42.8 % respectively. To supply two LO frequencies with 90º phase difference, a quadrature voltage controlled oscillator is designed using a series of coupling structure and accumulation mode PMOS varactors. The frequency tuning range is 2.304 GHz ~ 2.54 GHz when the control voltage changes from 0 to 0.7 V. The QVCO exhibits phase noise of -113 dBc/Hz at 600 kHz offset frequency and -119 dBc.Hz at 1 MHz offset frequency. All the circuits were designed in TSMC-0.18μm 1.8 V CMOS technology and simulated using HSPICE RF simulator.

A 5G mm-wave compact voltage-controlled oscillator in 0.25 µm pHEMT technology

A 5G mm-wave monolithic microwave integrated circuit (MMIC) voltage-controlled oscillator (VCO) is presented in this paper. It is designed on GaAs substrate and with 0.25 µm-pHEMT technology from UMS foundry and it is based on pHEMT varactors in order to achieve a very small chip size. A 0dBm-output power over the entire tuning range from 27.67 GHz to 28.91 GHz, a phase noise of -96.274 dBc/Hz and -116.24 dBc/Hz at 1 and 10 MHz offset frequency from the carrier respectively are obtained on simulation. A power consumption of 111 mW is obtained for a chip size of 0.268 mm2. According to our knowledge, this circuit occupies the smallest surface area compared to pHEMTs oscillators published in the literature.

III-Nitride nanophotonics for beyond-octave soliton generation and self-referencing

Frequency microcombs, successors to mode-locked laser and fiber combs, enable miniature rulersof light for applications including precision metrology, molecular fingerprinting and exoplanet discoveries. To enable frequency ruling functions, microcombs must be stabilized by locking their carrier-envelop offset frequency. So far, the microcomb stabilization remains compounded by the elaborate optics external to the chip, thus evading its scaling benefit. To address this challenge, here we demonstrate a nanophotonic chip solution based on aluminum nitride thin films, which simultaneously offer optical Kerr nonlinearity for generating octave soliton combs and Pockels nonlinearity for enabling heterodyne detection of the offset frequency. The agile dispersion control of crystalline III-Nitride photonics permits high-fidelity generation of solitons with features including 1.5-octave spectral span, dual dispersive waves and sub-terahertz repetition rates down to 220 gigahertz. These attractive characteristics, aided by on-chip phase-matched aluminum nitride waveguides, allow the full determination of the offset frequency. Our proof-of-principle demonstration represents an important milestone towards fully-integrated self-locked microcombs for portable optical atomic clocks and frequency synthesizers