Precision radial velocity measurement requires spectral calibration sources that exhibit short to long term wavelength stability and high modal density. Here we report on our efforts to develop a novel 400-1800 nm whispering gallery mode resonator etalon for calibration of optical or infrared spectrographs. The small crystalline MgF2 ring etalon is stable to better than 10-11 levels on 1 s timescales but requires environmental isolation and an referencing to an external standard to maintain long term performance. We will summarize our efforts thus far, as well as the performance achieved over 10 day measurements.
The Laser Interferometer Space Antenna (LISA), with its extreme distance measurement requirements (pm over arm lengths of 2.5 Mio km), imposes many stringent requirements on the laser sources used for interferometry. Frequency and power stability, as well as the side band phase noise represent considerable technological challenges, that must be maintained over the full 12.5 years mission duration. These constraints demand a streamlined laser design and a particular attention to reliability and procurement strategy, which poses a significant challenge. The main requirements for the laser critical sub-system have been analyzed. The Centre Suisse d’Electronique et de Microtechnique (CSEM), in the frame of a European Space Agency activity, was mandated to demonstrate a laser head for the LISA mission based on an alternative laser oscillator approach that does not rely on the LISA-baseline technology (i.e. Nd:YAG NPRO laser). The activity was named MONALISA. After a presentation of the key laser head requirements, the laser head design is described. A comprehensive test campaign was performed, and test results are presented.
Narrow-linewidth lasers operating in the near-infrared provide precise timing synchronization for atomic optical clocks and quantum computers. Crystalline ultra-high-Q optical resonators enable high-performance laser design in a small form factor that allow miniaturization of the devices using the lasers. Here we demonstrate a 780 nm self-injection-locked laser with Hertz-level instantaneous linewidth under single-mode continuous-wave operation. The self-injection locking induced by the whispering gallery mode resonator suppresses the frequency noise and reduces the drift of the free running device.
We report on our recent experiments involving tight packaging of RF photonic oscillators based on optical Kerr frequency combs generated in nonlinear optical microresonators. The devices with volume not exceeding one cubic centimeter characterized with phase noise approaching -120 dBc/Hz at 10 kHz frequency offset are demonstrated at 26 GHz and 28 GHz. Possibilities of tuning the oscillators with a piezo-actuator are discussed.
Interband and Quantum Cascade Lasers are key sources for MIR molecular sensing. Understanding their noise features and stabilizing their emission is of fundamental importance for applications like precision spectroscopy and metrology. High-Q crystalline Whispering Gallery Mode Resonators have proven to be powerful tools for characterization and stabilization of lasers from the UV to the MIR. Here, we report our recent results on Whispering Gallery Mode Resonators used for frequency characterization, stabilization and linewidth narrowing of Interband and Quantum Cascade Lasers. These results pave the way to new classes of compact MIR sources usable in Space missions, Metrology and Fundamental Physics.
We report on a study of performance of both active and passive optical gyroscopes based on high finesse crystalline whispering gallery mode (WGM) resonators. We show that the sensitivity of the devices is ultimately limited due to the nonlinearity of the resonator host material. A gyroscope characterized with 0.02 deg/hr^1/2 angle random walk and 2 deg/hr bias drift is demonstrated.
Narrow-linewidth lasers are key elements in optical metrology and spectroscopy. From their spectral purity, the measurements accuracy and the overall quality of collected data critically depend. Crystalline micro-resonators have undergone an impressive development in the last decade, opening new ways to photonics from the mm to the μm scale. Their wide transparency range and high Q-factor make them suitable for integration in compact apparatuses for precision spectroscopy from the visible to the mid-IR. Here, we present our recent results on frequency stabilization and linewidth narrowing of quantum cascade lasers using crystalline Whispering Gallery Mode Resonators for mid-IR precision spectroscopy.
This paper presents a novel architecture for a high performance atomic clock based on the use of miniature optical whispering gallery mode (WGM) resonators. Following the approach of stabilizing a laser local oscillator to an optical transition in an atom or ion, as used in advanced atomic clock, a semiconductor laser is used for stabilization to the D1 line of Rb atoms, held in a small vapor cell. The laser is self-injection locked to a WGM resonator to reduce its linewidth. To produce the RF output of the clock, a second WGM resonator excited with a second cw semiconductor laser produces an optical frequency comb that is demodulated on a fast photodiode. Locking the resonator that generates the frequency comb to the laser stabilized to the Rb transition transfers the stability of the atomic transition to the RF output of the clock. In this way, a miniature all-optical atomic clock is realized. Details of the operation of the clock and application of the architecture to other atomic systems, such as a ytterbium ion, will be described.
We demonstrate a free running 10 GHz microresonator-based RF photonic hyper-parametric oscillator characterized with phase noise better than -60 dBc/Hz at 10 Hz, -90 dBc/Hz at 100 Hz, and -150 dBc/Hz at 10 MHz. The device consumes less than 25 mW of optical power. A correlation between the frequency of the continuous wave laser pumping the nonlinear resonator and the generated RF frequency is confirmed. The performance of the device is compared with the performance of a standard optical fiber based coupled opto-electronic oscillator of OEwaves.
We discuss our recent progress in iimproving the phase noise of a semiconductor laser using self-injection locking of to a mode of a high-Q whispering gallery mode resonator. Locking efficiency is analyzed for semiconductor distributed feedback (DFB) as well as Fabry-Perot (FP) lasers operating at 690 nm, 1060 nm, 1550 nm, and 2 μm. Instantaneous linewidth below 300 Hz is realized with telecom DFB lasers. Tunability of the lasers is demonstrated. Commercially available packaged ”plug-and-play” devices are manufactured.
We report on the realization of a compact-package (44x27x14mm) narrow linewidth laser based on self-injection
locking of a distributed feedback semiconductor diode laser to a high-Q whispering gallery mode resonator
fabricated with electro-optic material. The packaged device operates at 1,550 nm and offers instantaneous
spectral linewidth performance smaller than 1.8 kHz for 3 mW of output power. We are able to tune the laser
frequency by applying voltage to the resonator. This suggest that the technology enables fabrication of ultra
narrow linewidth semiconductor lasers in a broad wavelength range of 390 nm to 2,900 nm. The laser source in a
compact footprint enables a multitude of sensing, monitoring, and metrology applications where high resolution
and precision and absolute accuracy are required.
In this paper we report on recent improvements in phase noise and frequency stability of a 10 GHz opto-electronic oscillator. In our OEO loop, the high Q elements (the optical fiber and the narrow bandpass microwave filter) are thermally stabilized using resistive heaters and temperature controllers, keeping their temperature above ambient. The thermally stabilized free running OEO demonstrates a short-term frequency stability of 0.02 ppm (over several hours) and frequency vs. temperature slope of −0.1 ppm/°C (compared to -8.3 ppm/°C for non thermally stabilized OEO). We obtained an exceptional spectral purity with phase noise level of -143 dBc/Hz at 10 kHz of offset frequency. We also describe the multi-loop configuration that reduces dramatically the spurious level at offset frequencies related to the loop round trip harmonic frequency. The multi-loop configuration has stronger mode selectivity due to interference between signals having different cavity lengths. A drop of the spurious level below −90 dBc was demonstrated. The effect of the oscillator aging on the frequency stability was studied as well by recording the oscillator frequency (in a chamber) over several weeks. We observed reversal in aging direction with logarithmic behavior of A ln(B t+1)-C ln(D t+1), where t is the time and A, B, C, D are constants. Initially, in the first several days, the positive aging dominates. However, later the negative aging mechanism dominates. We have concluded that the long-term aging behavioral model is consistent with the experimental results.
A semiconductor electron-hole plasma effectively reflects microwave radiation that is used in electromagnetic shields and semiconductor millimeter wave antennas. Silicon-based P- I-N structures allow us to engage in engineering the conductive properties of plasma crated under current injection. We calculate the I-V characteristics of short P- I-N structures and model their reflective properties in the millimeter wave band.
A new friend foe identification tag based on photonic band structure (PBS) is presented. The tag utilizes frequency-coded radar signal return. Targets that include the passive tag responds selectively to slightly different frequencies generated by interrogating MMW radar. It is possible to use in- and out-of-band gap frequencies or defect modes of the PBS in order to obtain frequency dependent radar waves reflections. This tag can be made in the form of patch attachable such as plate or corner reflectors, to be worn by an individual marine, or to be integrated into the platform camouflage. Ultimately, it can be incorporated as smart skin or a ground or airborne vehicle. The proposed tag takes full advantage of existing sensors for interrogation (minimal chances required), it is lightweight and small in dimensions, it operates in degraded environments, it has no impact on platform vulnerability, it has low susceptibility to spoofing and mimicking (code of the day) and it has low susceptibility to active jamming. We demonstrated the operation of the tag using multi-layer dielectric (Duroid) having periodic structure of metal on top of each of the layers (metal strips in this case). The experimental results are consistent with numerical simulation. The device can be combined with temporal coding to increase target detection and identification resolution.
We analyzed the feasibility of an all-weather, low-cost millimeter wave sensor for the detection of obstacles on the paths of the trains. We formulated the requirements for such a sensor and experimentally demonstrated radar detection of vehicles and trains.
Current trends in device miniaturization and integration, especially in the development of microwave monolithic integrated circuits, calls for flexible, arbitrarily shaped and curved interconnects. Standard dielectric waveguides and microstrip lines are subject to prohibitive losses and their functionality is limited because of their unflexible structures. The problem is addressed by confining the wave- guiding path in a substrate with a Photonic Band Gap structure in a manner that will result in the guided mode being localized within the band gap. Two devices implementing Photonic Band Structures for millimeter waves confinement are presented. The first waveguide is a linear defect in triangular lattice created in a silicon slab (TE mode). The structure consists of parallel air holes of circular cross sections. The silicon was laser drilled to create the 2D crystal. The second device consists of alumina rods arranged in a triangular lattice, surrounded by air and sandwiched between two parallel metal plates (TM mode). Electromagnetic wave (W-band) confinement was obtained in both devices for straight and bent waveguides. Three branch waveguides (intersecting line defects) was studied as well. Measurements confirmed the lowloss waveguide confinement property of the utilizing Photonic Band Gap structure. This structure can find applications in power combiner/splitter and other millimeter wave devices.
The previously demonstrated beam-forming PIPG (photo-induced plasma-grating) technology was used to design a beam- steering antenna operating at X-band and a 2D tracking antenna operating at W-band. Both antennas possess entire optoelectronics control.
Dielectric planar waveguides have been proven to be useful for MMW devices such as fixed beam or beam-steering antennas. Previously we developed several antennas comprising planar dielectric and semiconductor waveguides. To form the beam inside the planar waveguide we used a feed based on tunnel coupling between the dielectric rod waveguide and the planar waveguide. In this paper we are presenting a simple analysis for this coupling and comparing it with the experiment.
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