Optical frequency synthesizer with an integrated erbium tunable laser.

Optical frequency synthesizers have widespread applications in optical spectroscopy, frequency metrology, and many other fields. However, their applicability is currently limited by size, cost, and power consumption. Silicon photonics technology, which is compatible with complementary-metal-oxide-semiconductor fabrication processes, provides a low-cost, compact size, lightweight, and low-power-consumption solution. In this work, we demonstrate an optical frequency synthesizer using a fully integrated silicon-based tunable laser. The synthesizer can be self-calibrated by tuning the repetition rate of the internal mode-locked laser. A 20 nm tuning range from 1544 to 1564 nm is achieved with ~10-13 frequency instability at 10 s averaging time. Its flexibility and fast reconfigurability are also demonstrated by fine tuning the synthesizer and generating arbitrary specified patterns over time-frequency coordinates. This work promotes the frequency stability of silicon-based integrated tunable lasers and paves the way toward chip-scale low-cost optical frequency synthesizers

Integrated mode-locked lasers in a CMOS-compatible silicon photonic platform

CLEO: Science and Innovations 2015 San Jose, California United States 10–15 May 2015 ISBN: 978-1-55752-968-8 From the session: Silicon Photonic Systems (SM2I)The final version is available from the publisher via the DOI in this record.Integrated components necessary for a mode-locked laser are demonstrated on a platform that allows for monolithic integration with active silicon photonics and CMOS circuitry. CW lasing and Q-switched mode-locking are observed in the full structures.This work was supported under the DARPA E-PHI project, grant no. HR0011-12-2-0007

Ultra-narrow-linewidth erbium-doped lasers on a silicon photonics platform

This is the final published version. Available from the publisher via the DOI in this record.Event: Silicon Photonics XIII; 1053712, SPIE OPTO, 2018, San Francisco, California, United StatesWe report ultra-narrow-linewidth erbium-doped aluminum oxide (Al2O3:Er3+) distributed feedback (DFB) lasers with a wavelength-insensitive silicon-compatible waveguide design. The waveguide consists of five silicon nitride (SiNx) segments buried under silicon dioxide (SiO2) with a layer Al2O3:Er3+ deposited on top. This design has a high confinement factor (> 85%) and a near perfect (> 98%) intensity overlap for an octave-spanning range across near infrared wavelengths (950–2000 nm). We compare the performance of DFB lasers in discrete quarter phase shifted (QPS) cavity and distributed phase shifted (DPS) cavity. Using QPS-DFB configuration, we obtain maximum output powers of 0.41 mW, 0.76 mW, and 0.47 mW at widely spaced wavelengths within both the C and L bands of the erbium gain spectrum (1536 nm, 1566 nm, and 1596 nm). In a DPS cavity, we achieve an order of magnitude improvement in maximum output power (5.43 mW) and a side mode suppression ratio (SMSR) of > 59.4 dB at an emission wavelength of 1565 nm. We observe an ultra-narrow linewidth of ΔνDPS = 5.3 ± 0.3 kHz for the DPS-DFB laser, as compared to ΔνQPS = 30.4 ± 1.1 kHz for the QPS-DFB laser, measured by a recirculating self-heterodyne delayed interferometer (RSHDI). Even narrower linewidth can be achieved by mechanical stabilization of the setup, increasing the pump absorption efficiency, increasing the output power, or enhancing the cavity Q.This work is supported by the Defense Advanced Research Projects Agency (DARPA) Microsystems Technology Office’s (MTO) E-PHI (HR0011-12-2-0007) project. N. Li acknowledges a fellowship from the Agency of Science, Technology and Research (A*STAR), Singapore

Frequency Domain Spectroscopy in Rare-Earth-Doped Gain Media

Many spectroscopic techniques today rely on time-resolved measurements under short excitation pulses. Instead of using a chopped pump excitation, or ultrafast optical pulses, we expand on and apply the previously developed set of frequency domain methods to analyze the population level dynamics in rare-earth-doped media. By identifying the full frequency response of the gain medium, this method can accurately yield excited state lifetimes and can also be used to estimate transition cross-sections. The accuracy of the frequency domain methods are verified with Er3+-and Tm3+-doped fibers, and an Al2O3:Tm3+ waveguide, recovering similar results as reported by time-resolved techniques. The complete frequency domain model presented here can be used in characterization of novel optical gain media, and can provide insights into population dynamics in solid state amplifiers and lasers

Integrated CMOS-compatible Q-switched mode-locked lasers at 1900nm with an on-chip artificial saturable absorber.

We present a CMOS-compatible, Q-switched mode-locked integrated laser operating at 1.9 µm with a compact footprint of 23.6 × 0.6 × 0.78mm. The Q-switching rate is 720 kHz, the mode-locking rate is 1.2 GHz, and the optical bandwidth is 17nm, which is sufficient to support pulses as short as 215 fs. The laser is fabricated using a silicon nitride on silicon dioxide 300-mm wafer platform, with thulium-doped Al2O3 glass as a gain material deposited over the silicon photonics chip. An integrated Kerr-nonlinearity-based artificial saturable absorber is implemented in silicon nitride. A broadband (over 100 nm) dispersion-compensating grating in silicon nitride provides sufficient anomalous dispersion to compensate for the normal dispersion of the other laser components, enabling femtosecond-level pulses. The laser has no off-chip components with the exception of the optical pump, allowing for easy co-integration of numerous other photonic devices such as supercontinuum generation and frequency doublers which together potentially enable fully on-chip frequency comb generation

Transmissive silicon photonic dichroic filters with spectrally selective waveguides

Many optical systems require broadband filters with sharp roll-offs for efficiently splitting or combining light across wide spectra. While free space dichroic filters can provide broadband selectivity, on-chip integration of these high-performance filters is crucial for the scalability of photonic applications in multi-octave interferometry, spectroscopy, and wideband wavelength-division multiplexing. Here we present the theory, design, and experimental characterization of integrated, transmissive, 1 × 2 port dichroic filters using spectrally selective waveguides. Mode evolution through adiabatic transitions in the demonstrated filters allows for single cutoff and flat-top responses with low insertion losses and octave-wide simulated bandwidths. Filters with cutoffs around 1550 and 2100 nm are fabricated on a silicon-on-insulator platform with standard complementary metal-oxide-semiconductor processes. A filter roll-off of 2.82 dB nm−1 is achieved while maintaining ultra-broadband operation. This new class of nanophotonic dichroic filters can lead to new paradigms in on-chip communications, sensing, imaging, optical synthesis, and display applications

Ultra-narrow-linewidth Al2O3:Er3 lasers with a wavelength-insensitive waveguide design on a wafer-scale silicon nitride platform

This is the author accepted manuscript. The final version is freely available on open access from Optical Society of America via the DOI in this record.We report ultra-narrow-linewidth erbium-doped aluminum oxide (Al2O3:Er3+) distributed feedback (DFB) lasers with a wavelength-insensitive silicon-compatible waveguide design. The waveguide consists of five silicon nitride (SiNx) segments buried under silicon dioxide (SiO2) with a layer Al2O3:Er3+ deposited on top. This design has a high confinement factor (> 85%) and a near perfect (> 98%) intensity overlap for an octave-spanning range across near infra-red wavelengths (950–2000 nm). We compare the performance of DFB lasers in discrete quarter phase shifted (QPS) cavity and distributed phase shifted (DPS) cavity. Using QPS-DFB configuration, we obtain maximum output powers of 0.41 mW, 0.76 mW, and 0.47 mW at widely spaced wavelengths within both the C and L bands of the erbium gain spectrum (1536 nm, 1566 nm, and 1596 nm). In a DPS cavity, we achieve an order of magnitude improvement in maximum output power (5.43 mW) and a side mode suppression ratio (SMSR) of > 59.4 dB at an emission wavelength of 1565 nm. We observe an ultra-narrow linewidth of ΔνDPS = 5.3 ± 0.3 kHz for the DPS-DFB laser, as compared to ΔνQPS = 30.4 ± 1.1 kHz for the QPS-DFB laser, measured by a recirculating self-heterodyne delayed interferometer (R-SHDI).Defense Advanced Research Projects Agency (DARPA) E-PHI (grant no. HR0011-12-2-0007) project

Monolithically-integrated distributed feedback laser compatible with CMOS processing.

An optically-pumped, integrated distributed feedback laser is demonstrated using a CMOS compatible process, where a record-low-temperature deposited gain medium enables integration with active devices such as modulators and detectors. A pump threshold of 24.9 mW and a slope efficiency of 1.3 % is demonstrated at the lasing wavelength of 1552.98 nm. The rare-earth-doped aluminum oxide, used as the gain medium in this laser, is deposited by a substrate-bias-assisted reactive sputtering process. This process yields optical quality films with 0.1 dB/cm background loss at the deposition temperature of 250 °C, and therefore is fully compatible as a back-end-of-line CMOS process. The aforementioned laser's performance is comparable to previous lasers having gain media fabricated at much higher temperatures (> 550 °C). This work marks a crucial step towards monolithic integration of amplifiers and lasers in silicon microphotonic systems