Conference on Lasers and Electro-Optics

Frequency-tuned continuous true-time delay by optical coherent transient technology

K.D. Merkel, William Randall Babbitt

Published Jan 20, 2003• 0 citations

Abstract

Summary form only given. A practical device creating a variable RF true-time delay (TTD) for signals on an optical carrier would be useful in array antennas. An optical coherent transient (OCT)-TTD device could provide high-resolution delays (/spl sim/1 ps) over a wide range (/spl sim/1 /spl mu/s), for high bandwidth signals (/spl sim/10 GHz) with currently available materials. In previously demonstrated OCT-TTD devices, two optical pulses separated in time and space program a delay in an absorbing medium as a spatial-spectral grating on an inhomogeneously broadened transition (IBT). In the paper, we experimentally demonstrate widely tunable OCT-TTD of a continuous optical data stream without changing the timing between the programming pulses.

DOI: 10.1109/cleo.1999.834042

Related papers

Temporal dependence of coherent transient regenerated true-time delays on intensity of applied pulses

K.D. Merkel, William Randall Babbitt

Summary form only given. Accurate true-time delays are essential to correctly steer modern phased-array antennas. Optical coherent transient technology has the ability to store a variable true-time delay as a spatial-spectral holographic population grating in an inhomogeneously broadened absorber (IBA). Typically, two optical pulses program the delay. A third optical pulse or waveform applied to the IBA generates a delayed replica of itself. The delay is typically defined by /spl tau//sub 21/=t/sub 2/-t/sub 1/, the arrival time difference of the first two pulses. However, we find that this prediction for the delay of the emitted signal only holds for input optical pulse areas much less than pi. Experimental investigation and simulations were performed to observe the variation in arrival time of the output signal.

Conference on Lasers and Electro-OpticsJan 1, 19980 citations

Broadband true time-delay with optical coherent transients

Ming Tian, Randy R. Reibel, William Randall Babbitt

Summary form only given. When phased array antenna systems operate with broadband (multiple gigahertz) signals, true time-delay devices are needed to solve the problem of beam squint. Optical coherent transient technology, also known as spatial-spectral holography, offers a unique way of using the space and frequency dimensions of inhomogeneously broadened absorbers to handle thousands of high-resolution delays in a compact volume. We demonstrated broadband true-time delay in a Tm/sup 3+/:YAG crystal, which offers delays up to a microsecond on signals having several tens of GHz bandwidth with sub-picosecond delay resolution.

Conference on Lasers and Electro-OpticsJan 1, 20010 citations

Signal correlator with programmable variable time delay based on optical coherent transients

K.D. Merkel, Zachary Cole, William Randall Babbitt

We have demonstrated a technique for programming variable time delays of a pattern waveform in a spectral grating. By frequency shifting the chirped programming pulses, correlation and delays over 450 ns were achieved without changing the programming sequence timing. The demonstrated bandwidth of 40 MHz only utilized /spl sim/0.2 % of the inhomogeneously broadened absorber's bandwidth. Thus, this technique has the potential to allow versatile, all-optical reception and processing of > 10 GHz signals in broadband array antenna beamforming.

IEEE Lasers and Electro-Optics Society Annual Meeting (LEOS)Jan 20, 20030 citations

Variable-time-delay optical coherent transient signal processing

K.D. Merkel, William Randall Babbitt, Ken E. Anderson +1 more

A technique is proposed and experimentally demonstrated that achieves simultaneous optical pattern waveform storage and programmable time delay for continuous real-time signal processing by use of optical coherent transient technology. We achieve variable-time-delay and broadband signal processing by frequency shifting of two chirped programming pulses, the chirp rate of one being twice that of the other, without using brief reference pulses and without changing the timing of the programming sequence. We demonstrate the technique experimentally in Tm(3+): YAG at 5 K for 40-MHz chirps by performing temporal signal convolution with true-time delays that vary over a 250-ns range.

Optics LettersOct 15, 199910 citations

Demonstration of optical coherent transient true-time delay at 4 Gbits/s

Ming Tian, Randy R. Reibel, William Randall Babbitt

Multigigabit-per-second true time delay (TTD) was experimentally demonstrated by use of optical coherent transient techniques in a Tm(3+):YAG crystal. A delay accuracy of 1 ps and a delay resolution of 7 ps (both measurement limited) were achieved. The retrieved data retained good fidelity.

Optics LettersAug 1, 200117 citations

Tunable Optical True-Time Delay Devices Would Exploit EIT

Igor K. Kulikov, L.D. DiDomenico, Hwang Lee

Tunable optical true-time delay devices that would exploit electromagnetically induced transparency (EIT) have been proposed. Relative to prior true-time delay devices (for example, devices based on ferroelectric and ferromagnetic materials) and electronically controlled phase shifters, the proposed devices would offer much greater bandwidths. In a typical envisioned application, an optical pulse would be modulated with an ultra-wideband radio-frequency (RF) signal that would convey the information that one seeks to communicate, and it would be required to couple differently delayed replicas of the RF signal to the radiating elements of a phased-array antenna. One or more of the proposed devices would be used to impose the delays and/or generate the delayed replicas of the RF-modulated optical pulse. The beam radiated or received by the antenna would be steered by use of a microprocessor-based control system that would adjust operational parameters of the devices to tune the delays to the required values. EIT is a nonlinear quantum optical interference effect that enables the propagation of light through an initially opaque medium. A suitable medium must have, among other properties, three quantum states (see Figure 1): an excited state (state 3), an upper ground state (state 2), and a lower ground state (state 1). These three states must form a closed system that exhibits no decays to other states in the presence of either or both of two laser beams: (1) a probe beam having the wavelength corresponding to the photon energy equal to the energy difference between states 3 and 1; and (2) a coupling beam having the wavelength corresponding to the photon energy equal to the energy difference between states 3 and 2. The probe beam is the one that is pulsed and modulated with an RF signal.

Oct 1, 20040 citations