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White J.O.,U.S. Army | Vasilyev A.,California Institute of Technology | Cahill J.P.,U.S. Army | Satyan N.,California Institute of Technology | And 4 more authors.
Optics Express | Year: 2012

The output of high power fiber amplifiers is typically limited by stimulated Brillouin scattering (SBS). An analysis of SBS with a chirped pump laser indicates that a chirp of 2.5 × 1015 Hz/s could raise, by an order of magnitude, the SBS threshold of a 20-m fiber. A diode laser with a constant output power and a linear chirp of 5 × 1015 Hz/s has been previously demonstrated. In a low-power proof-of-concept experiment, the threshold for SBS in a 6-km fiber is increased by a factor of 100 with a chirp of 5 × 1014 Hz/s. A linear chirp will enable straightforward coherent combination of multiple fiber amplifiers, with electronic compensation of path length differences on the order of 0.2 m. ©2012 Optical Society of America.


Satyan N.,California Institute of Technology | Vasilyev A.,California Institute of Technology | Rakuljic G.,Telaris Inc. | White J.O.,U.S. Army | Yariv A.,California Institute of Technology
Optics Express | Year: 2012

We propose, analyze and demonstrate the optoelectronic phase-locking of optical waves whose frequencies are chirped continuously and rapidly with time. The optical waves are derived from a common optoelectronic swept-frequency laser based on a semiconductor laser in a negative feedback loop, with a precisely linear frequency chirp of 400 GHz in 2 ms. In contrast to monochromatic waves, a differential delay between two linearly chirped optical waves results in a mutual frequency difference, and an acoustooptic frequency shifter is therefore used to phase-lock the two waves. We demonstrate and characterize homodyne and heterodyne optical phase-locked loops with rapidly chirped waves, and show the ability to precisely control the phase of the chirped optical waveform using a digital electronic oscillator. A loop bandwidth of ∼ 60 kHz, and a residual phase error variance of < 0.01 rad2 between the chirped waves is obtained. Further, we demonstrate the simultaneous phase-locking of two optical paths to a common master waveform, and the ability to electronically control the resultant two-element optical phased array. The results of this work enable coherent power combining of high-power fiber amplifiers-where a rapidly chirping seed laser reduces stimulated Brillouin scattering-and electronic beam steering of chirped optical waves. © 2012 Optical Society of America.


Vasilyev A.,California Institute of Technology | Petersen E.,U.S. Army | Satyan N.,California Institute of Technology | Rakuljic G.,Telaris Inc. | And 2 more authors.
IEEE Photonics Technology Letters | Year: 2013

Using a rapidly-chirped (5× 1014 Hz s) continuous-wave optoelectronic swept-frequency seed laser and two 3 W erbium-doped fiber amplifiers, we demonstrate simultaneous stimulated Brillouin scattering suppression, coherent power combining, and electronic beam steering, without imposing strict path-length matching requirements. Our platform presents a viable path toward high-power continuous-wave sources. © 1989-2012 IEEE.


Vasilyev A.,California Institute of Technology | Satyan N.,California Institute of Technology | Xu S.,California Institute of Technology | Rakuljic G.,Telaris Inc. | Yariv A.,California Institute of Technology
Applied Optics | Year: 2010

We propose and demonstrate a novel approach to increase the effective bandwidth of a frequencymodulated continuous-wave (FMCW) ranging system. This is achieved by algorithmically stitching together the swept spectra of separate laser sources. The result is an improvement in the range resolution proportional to the increase in the swept-frequency range. An analysis of this system as well as the outline of the stitching algorithm are presented. Using three distinct swept-frequency optical waveforms, we experimentally demonstrate a threefold improvement in the range resolution of a three-sweep approach over the conventional FMCW method. © 2010 Optical Society of America.


Satyan N.,California Institute of Technology | Rakuljic G.,Telaris Inc. | Yariv A.,California Institute of Technology
Journal of Lightwave Technology | Year: 2010

We present an analysis and demonstration of the doubling of the chirp rate and total chirp bandwidth of a frequency chirped optical signal by the process of four-wave mixing in a non-linear optical medium. The effects of chromatic dispersion and input power on the maximum achievable output bandwidth are analyzed, and a dispersion compensation technique for phase matching is described. The doubling of an input linear frequency sweep of 100 GHz/1 ms in a highly nonlinear optical fiber is experimentally demonstrated. Further, it is proposed that a cascaded implementation of the four-wave mixing process leads to a geometric increase in the bandwidth of the frequency chirp. With an electronically tuned chirped laser at the input stage, this process can be used to generate extremely wideband swept frequency sources with no moving parts, for applications in high-speed and high-resolution optical imaging and spectroscopy. © 2006 IEEE.


Patent
California Institute of Technology and Telaris Inc. | Date: 2014-12-30

A detection apparatus and method for FMCW LIDAR employ signals whose frequencies are modified so that low-cost and low-speed photodetector arrays, such as CCD or CMOS cameras, can be employed for range detection. The LIDAR is designed to measure the range z to a target and includes a single mode swept frequency laser (SFL), whose optical frequency is varied with time, as a result of which, a target beam which is reflected back by the target is shifted in frequency from a reference beam by an amount that is proportional to the relative range z to the target. The reflected target beam is combined with the reference beam and detected by the photodetector array. By first modulating at least one of the target and reference beams such that the difference between the frequencies of the reflected target beam and the reference beam is reduced to a level that is within the bandwidth of the photodetector array, the need for high-speed detector arrays for full-field imaging is obviated.


Grant
Agency: Department of Defense | Branch: Army | Program: STTR | Phase: Phase II | Award Amount: 503.90K | Year: 2015

Spontaneous emission is a quantum mechanical process that represents the main source of phase noise in state-of-the-art semiconductor lasers, limiting their coherence, and their suitability for high-speed communication and sensing applications. This proposal aims to develop ultra-high coherence semiconductor lasers on the Silicon/III-V platform with a quantum linewidth of


Grant
Agency: Department of Defense | Branch: Army | Program: STTR | Phase: Phase I | Award Amount: 150.00K | Year: 2014

Spontaneous emission is a quantum mechanical process that represents the main source of phase noise in state-of-the-art semiconductor lasers, limiting their coherence, and their suitability for high-speed communication and sensing applications. This proposal aims to develop ultra-high coherence semiconductor lasers on the Silicon/III-V platform with a quantum linewidth of<20 kHz (Phase I) and<5 kHz (Phase II), by tackling this root cause of phase noise in the laser. The laser incorporates two novel concepts to overcome the effects of spontaneous emission: (i) suppression of the quantum noise at its source, by controlling the rate of spontaneous emission; and (ii) mitigation of the effect of the spontaneous emission on the coherence of the laser. Low-cost, wafer-scale, high-throughput techniques will be developed and employed in the fabrication of the laser. The development of this laser on a CMOS compatible silicon platform enables the integration of the laser with other passive and active optical elements and electronics; and its small form factor and low power consumption make it a scalable solution for next-generation high-speed coherent communication and sensing applications.


Patent
California Institute of Technology and Telaris Inc. | Date: 2016-02-05

A laser resonator includes an active material, which amplifies light associated with an optical gain of the resonator, and passive materials disposed in proximity with the active material. The resonator oscillates over one or more optical modes, each of which corresponds to a particular spatial energy distribution and resonant frequency. Based on a characteristic of the passive materials, for the particular spatial energy distribution corresponding to at least one of the optical modes, a preponderant portion of optical energy is distributed apart from the active material. The passive materials may include a low loss material, which stores the preponderant optical energy portion distributed apart from the active material, and a buffer material disposed between the low loss material and the active material, which controls a ratio of the optical energy stored in the low loss material to a portion of the optical energy in the active material. A Vernier grating and tuning mechanism can be used to tune the low-noise laser.


Patent
Telaris Inc. and California Institute of Technology | Date: 2013-10-09

A detection apparatus and method for FMCW LIDAR employ signals that are modified so that low-cost and low-speed photodetector arrays, such as CCD or CMOS cameras, can be employed for range detection. The LIDAR is designed to measure the range to one or more targets and includes a single mode swept frequency laser (SFL), whose optical frequency is varied with time, as a result of which, a target beam which is reflected back by the one or more targets is shifted in frequency from a reference beam by an amount that is proportional to the relative range to the one or more targets. The reflected target beam(s) is/are combined with the reference beam and detected by the photodetector array. In the case of a sparse number of targets to be detected, Compressive Sensing (CS) techniques can be employed by a processor to reduce the number of measurements necessary to determine the range of each target.

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