Simple-structured, subfemtosecond-resolution optical-microwave phase detector

Abstract

We demonstrate a simple all-fiber photonic phase detector that can measure the phase (timing) difference between an optical pulse train and a microwave signal with subfemtosecond resolution and -60 dB-level amplitude-to-phase conversion coefficient. It is based on passive phase biasing of a Sagnac loop by the intrinsic phase shift of a symmetric 3×3 fiber coupler. By eliminating the necessity of magneto-optic components or complex radio frequency (RF) electronics for phase biasing of the Sagnac loop, this phase detector has potential to be implemented as an integrated photonic device as well. When using this device for synchronization between a 250 MHz mode-locked Er-fiber laser and an 8 GHz microwave oscillator, the minimum residual phase noise floor reaches <-154 dBc/Hz (at 8 GHz carrier) with integrated root mean square (rms) timing jitter of 0.97 fs [1 Hz-1 MHz]. The long-term rms timing drift and frequency instability are 0.92 fs (over 5000 s) and 4×10 (at 10,000 s averaging time), respectively.

Microwave Photonic Radars

“…Previously, the highly coherent pulse source was employed for developing a number of new techniques for radar applications, such as low-noise microwave signal generation [166], [167], optical sampling and ADC [112], [168], [169], Fourier transform [170], [171], phase detection [172]- [174], time delay measurement [175], synchronizations [173], [176], etc. Most of them can achieve extreme performance in some aspects which is impossible for pure electronic approaches.…”

Ultra-precise timing and synchronization for large-scale scientific instruments

“…On the other hand, since mode-locked lasers can provide an ultrashort pulse train with ultralow timing jitter, such an "optically assisted" phase detection can provide much higher resolution for microwave phase discrimination. In the past decades, several kinds of optical-microwave phase detectors have been demonstrated [44][45][46][47][48][49][50][51][52]. Figure 5 shows the architecture of a free-space-coupled balanced optical-microwave phase detector (BOMPD), which was first proposed in Refs.…”

“…In Ref. [51], a simple 3 × 3 fiber coupler structure is introduced, so the π∕2 phase bias condition is automatically maintained for a Sagnac loop. In all these schemes, the phase error signal is encoded in the mode-locked laser's baseband power change; thus, a balanced detection is necessary to remove the laser's high average power.…”

“…It can be implemented using the techniques discussed in this paper. For example, timing link stabilization by [47,61,[81][82][83], the synchronization between the microwave reference and master laser, master laser to klystron, linear accelerators, and bunch compressor by [44][45][46][47][48][49][50][51][52]61,88,91,92], master laser to injector laser, seed laser and seed oscillator of the probe laser by [34,35,38,39,47,61,87,90], probe laser seed oscillator to probe laser output by [62][63][64][65][66], and x-ray timing characterization by [58][59][60][61].…”

Attosecond electronic timing with rising edges of photocurrent pulses

“…Here, using an electro-optic sampling-based ultrasensitive timing detection method 27 , 28 , we characterize the excess timing jitter between the optical pulse train and the photocurrent pulse train with 51-as (r.m.s.) resolution over 1 MHz bandwidth.…”