Abstract
We demonstrate the first self-referenced full stabilization of a diode-pumped solid-state laser (DPSSL) frequency comb with a GHz repetition rate. The Yb:CALGO DPSSL delivers an average output power of up to 2.1 W with a typical pulse duration of 96 fs and a center wavelength of 1055 nm. A carrier-envelope offset (CEO) beat with a signal-to-noise ratio of 40 dB (in 10-kHz resolution bandwidth) is detected after supercontinuum generation and f-to-2f interferometry directly from the output of the oscillator, without any external amplification or pulse compression. The repetition rate is stabilized to a reference synthesizer with a residual integrated timing jitter of 249 fs [10 Hz - 1 MHz] and a relative frequency stability of 10-12/s. The CEO frequency is phase-locked to an external reference via pump current feedback using home-built modulation electronics. It achieves a loop bandwidth of ~150 kHz, which results in a tight CEO lock with a residual integrated phase noise of 680 mrad [1 Hz - 1 MHz]. We present a detailed characterization of the GHz frequency comb that combines a noise analysis of the repetition rate frep, of the CEO frequency fCEO, and of an optical comb line at 1030 nm obtained from a virtual beat with a narrow-linewidth laser at 1557 nm using a transfer oscillator. An optical comb linewidth of about 800 kHz is assessed at 1-s observation time, for which the dominant noise sources of frep and fCEO are identified.
Highlights
Fully-stabilized optical frequency combs from modelocked lasers have revolutionized many fields in optics and physics by enabling ultra-precise measurements and by providing a direct and coherent link between the optical and microwave spectral domains [1,2,3]
We present a detailed characterization of the GHz frequency comb that combines a noise analysis of the repetition rate frep, of the carrier-envelope offset (CEO) frequency fCEO, and of an optical comb line at 1030 nm obtained from a virtual beat with a narrow-linewidth laser at 1557 nm using a transfer oscillator
A CEO beat with a signal-to-noise ratio (SNR) of ~40 dB was detected in a resolution bandwidth (RBW) of 10 kHz (Fig. 4)
Summary
Fully-stabilized optical frequency combs from modelocked lasers have revolutionized many fields in optics and physics by enabling ultra-precise measurements and by providing a direct and coherent link between the optical and microwave spectral domains [1,2,3]. Frequency combs constitute today a key component in various applications ranging from optical frequency metrology [4,5] to ultra-high resolution broadband spectroscopy [6,7] and optical atomic clocks [8,9] that have become the most stable clocks existing today Some of these applications, such as the calibration of astronomical spectrographs [10,11] or the generation of ultra-low-noise microwave signals [12,13] can benefit from frequency combs with a high repetition rate, which provide a higher optical power per comb mode for a given average power and facilitate the spectral filtering of individual modes. A 15-GHz Yb:Y2O3 ceramic DPSSL was fully-stabilized by means of repetition rate locking on one side, and stabilization of one comb line to an ultra-stable laser using a feedforward stabilization on the other side [20] This comb was not self-referenced and suffers from the frequency drift of the reference laser in comparison to a CEO-stabilized comb. We show that the intensity noise of the pump diode and mechanical noise induced by its water cooling constitute the main contributions to the CEO phase noise
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