Laser phase-locked loop

Enloe, L. H.; Rodda, J.L.

doi:10.1109/proc.1965.3585

Cited by 77 publications

(22 citation statements)

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“…1,2 Various technologies have been explored to achieve the goal by using semiconductor (SC) lasers and fiber lasers. 1,[3][4][5][6][7][8] In this Letter we report what we believe to be the first coherent power addition of two commercial grade SC lasers by using current-injection optical phase-lock loops [9][10][11][12][13] (OPLLs). Compared with the previous coherent power-combining techniques, including the optical injection OPLLs, the current-injection OPLLs technique can provide individual electronic control of the frequency and phase of each laser in an array without external phase modulators and thus can lead to a big coherent emitting aperture that can be controlled, focused, distortion corrected, scanned in space, and pulsed by using pure electronic control.…”

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confidence: 89%

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Coherent combining of the output of two semiconductor lasers using optical phase-lock loops

Liang

Yariv

Kewitsch³

et al. 2007

Opt. Lett.

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confidence: 89%

“…Ever since the early pioneering work and demonstration of the first OPLL, 9 different types of lasers have been used to build OPLLs. [10][11][12][13] Compared with fiber lasers and solid state lasers, SC lasers are especially attractive for applications requiring high power and high efficiency.…”

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confidence: 99%

Coherent combining of the output of two semiconductor lasers using optical phase-lock loops

Liang

Yariv

Kewitsch³

et al. 2007

Opt. Lett.

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“…In the present work we report on the extension of these techniques to high power (~1W) Master Oscillator Power Amplifier (MOPA) SCLs phase-locked to a low power reference laser (~1mW). This work utilizes OPLLs in which control currents are injected directly into the DFB section of each MOPA [5][6][7] to modulate the optical frequency/phase of the MOPA. Under frequency and phase-lock conditions, the cw optical outputs of the two MOPAs are coherently combined and their mutual coherence is studied.…”

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confidence: 99%

Coherent power combination of two Master-oscillator-power-amplifier (MOPA) semiconductor lasers using optical phase lock loops

Liang¹,

Satyan²,

Yariv³

et al. 2007

Opt. Express

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Using heterodyne Optical Phase-Locked Loops (OPLLs), two 1W high power 1550 nm master-oscillator-power-amplifier (MOPA) semiconductor lasers operating as current controlled oscillators are phaselocked to a 1 mW reference laser. The signals of the two MOPAs are then coherently combined and their mutual coherence is studied. In each OPLL, the acquisition range is increased to +/-1.1GHz with the help of an aidedacquisition circuit. Control of the phase of a single slave MOPA is demonstrated using a RF phase shifter. The differential phase error between two MOPAs locked to the common reference laser is typically 22 degrees.

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“…In a typical OPLL the beat note of ML and SL is registered with a photodiode detector (PD) and then an electronic mixer is used for comparison of the phase with the reference local oscillator (LO) [22,23]. Such construction imposes severe limitations on the maximal phase error | | < ∕2 rad due to periodic response of the mixer.…”

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confidence: 99%

Optical frequency locked loop for long-term stabilization of broad-line DFB laser frequency difference

2017

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In multiple applications, phase coherence of the two laser fields locked at a frequency offset is not required [2][3][4][5][6][7][8][9][10][11] and a mere frequency lock is a sufficient solution. Nevertheless, one of the most commonly used solutions is the optical phase locked loop (OPLL) [12][13][14][15]. In a generic OPLL the master laser (ML) and the slave laser (SL) are combined and the beat note is measured on a fast photodiode (PD), compared with a reference value and then the difference is fed through the loop filter and used to tune SL by employing a fast current modulator. However, phase difference has to be kept within tight margins for OPLLs to work, rendering them impractical for broad-line lasers.If the OPLL is constructed to ensure only the frequency drift stabilization and not the phase coherence, it constitutes an optical frequency locked loop (OFLL). Such approach has been presented previously in Ref.[16]; however, it was applied to narrow-line external cavity diodes lasers (ECDL) and was based on a frequency voltage converter, allowing only up to 8 MHz offsets between SL and ML. OPLL setups involving phase-frequency detectors (PFD) have been presented in Refs. [17] or [18] but for frequency offsets only up to 7 GHz. Both works were concerned with phase coherence requiring complicated loop filters and either field programmable gate array (FPGA) implementation or two parallel proportional-integral (PI) controllers. Ivanov et. al. [18] apply their setup to DFB lasers albeit of narrower line (1 MHz) than in our case. They also present a detailed analysis of OPLL performance in the presence of frequency dividers.Here we present an OFLL designed for the stabilization of the long-term (>100 μs) frequency drift. Our setup is based on an integrated PFD chip that compares the beat note signal of ML and SL with low-frequency reference. The PD and PFD are specifically matched to provide the simplicity of setup construction and usage. AbstractWe present an experimental realization of the optical frequency locked loop applied to long-term frequency difference stabilization of broad-line DFB lasers along with a new independent method to characterize relative phase fluctuations of two lasers. The presented design is based on a fast photodiode matched with an integrated phase-frequency detector chip. The locking setup is digitally tunable in real time, insensitive to environmental perturbations and compatible with commercially available laser current control modules. We present a simple model and a quick method to optimize the loop for a given hardware relying exclusively on simple measurements in time domain.Step response of the system as well as phase characteristics closely agree with the theoretical model. Finally, frequency stabilization for offsets within 4-15 GHz working range achieving <0.1 Hz long-term stability of the beat note frequency for 500 s averaging time period is demonstrated. For these measurements we employ an I/Q mixer that allows us to precisely and independently measure the full phase tr...

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Laser phase-locked loop

Cited by 77 publications

References 1 publication

Coherent combining of the output of two semiconductor lasers using optical phase-lock loops

Coherent combining of the output of two semiconductor lasers using optical phase-lock loops

Coherent power combination of two Master-oscillator-power-amplifier (MOPA) semiconductor lasers using optical phase lock loops

Optical frequency locked loop for long-term stabilization of broad-line DFB laser frequency difference

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