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The authors report on stabilizing the carrier-envelope phase of mode-locked Ti:sapphire lasers. Optimization of the construction of the lasers for ease of phase stabilization is discussed. Results demonstrating long-term phase coherence of the generated pulse train are presented, yielding a phase coherence time of at least 326 s, measurement time limited. The conversion of amplitude noise to phase noise in the microstructured fiber, which is used to obtain an octave spanning spectrum, is measured. The resulting phase noise is found to be sufficiently small so as to not corrupt the phase stabilization. Shift of carrier-envelope phase external to the laser cavity due to propagation through a dispersive material is measured.

The comparison of optical atomic clocks with frequency instabilities reaching 1 part in 1016 at 1 s will enable more stringent tests of fundamental physics. These comparisons, mediated by optical frequency combs, require optical synthesis and measurement with a performance better than, or comparable to, the best optical clocks. Fiber-based mode-locked lasers have shown great potential for compact, robust, and efficient optical clockwork but typically require multiple amplifier and fiber optic paths that limit the achievable fractional frequency stability near 1 part in 1016 at 1 s. Here we describe an erbium-fiber laser frequency comb that overcomes these conventional challenges by ensuring that all critical fiber paths are common mode and within the servo-controlled feedback loop. Using this architecture, we demonstrate a fractional optical measurement uncertainty below 1×10−19 and fractional frequency instabilities less than 3×10−18 at 1 s and 1×10−19 at 1000 s.

We demonstrate an easy to manufacture, 25 mm long ultra-stable optical reference cavity for transportable photonic microwave generation systems. Employing a rigid holding geometry that is first-order insensitive to the squeezing force and a cavity geometry that improves the thermal noise limit at room temperature, we observe a laser phase noise that is nearly thermal noise limited for three frequency decades (1 Hz to 1 kHz offset) and supports 10 GHz generation with phase noise near -100 dBc/Hz at 1 Hz offset and 600 Hz. The fractional frequency stability reaches $2\times10^{-15}$ at 0.1 s of averaging., Comment: Letter

A stable optical frequency is phase-coherently divided to generate ultralow-noise 10 GHz signals having phase noise below -100 dBc/Hz at 1 Hz and a white noise of -177 dBc/Hz at higher offset frequencies. We discuss the technical and fundamental challenges of this approach, along with potential for integration of the components in a portable and robust system.

We describe noise limitations associated with Er:fiber-based optical frequency dividers. A low-noise Er:fiber laser combined with optimized photodetection results in 5 GHz signals having phase noise floors of -176 dBc/Hz.

Using modified uni-travelling carrier photodiodes that exhibit high linearity at high photocurrent we have generated a 10 GHz microwave carrier via optical frequency division with sub 500 attosecond absolute timing jitter (1Hz - 10 MHz).

Quantum state engineering of ultracold matter and precise control of optical fields have together allowed accurate measurement of light-matter interactions for applications in precision tests of fundamental physics. State-of-the-art lasers maintain optical phase coherence over one second. Optical frequency combs distribute this optical phase coherence across the entire visible and infrared parts of the electromagnetic spectrum, leading to the direct visualization and measurement of light ripples. At the same time, ultracold atoms confined in an optical lattice with zero differential ac Stark shift between two clock states allow us to minimize quantum decoherence while strengthening the clock signal. For Sr, we achieve a resonance quality factor >2.4 x 10 on the S0 – P0 doubly forbidden clock transition at 698 nm [1]. The uncertainty of this new clock has reached 1 x 10 and its instability approaches 1 x 10 at 1 s [2]. These developments represent a remarkable convergence of ultracold atoms, laser stabilization, and ultrafast science. Further improvements are still tantalizing, with quantum measurement and precision metrology combining forces to explore the next frontier.

Fabry-Perot cavity filtering of broadband optical frequency combs is studied experimentally and theoretically. Effects of dispersion, mirror coatings, and carrier envelope offset frequency are analyzed while highlighting applications to waveform generation and spectroscopic references.

We report tests of local position invariance (LPI) and constancy of fundamental constants from measurements of the frequency ratio of the 282-nm 199Hg+ optical clock transition to the ground-state hyperfine splitting in 133Cs. Analysis of the frequency ratio, extending over six years at NIST, is used to place a limit on the fractional variation of the two clocks of less than 5.8times10-6 per change in normalized solar gravitational potential, and a limit on fractional variation of the fine structure constant at alpha dot/alpha < 1.3x10-16 yr-1, assuming invariance of other fundamental constants. Comparison of our results with those previously reported for the absolute optical frequency measurements of coupled 171Yb+ versus other constraint 133Cs standard yields a coupled constraint of -0.04times10-15 < alpha dot/alpha < 0.46times10-15 yr-1 and -2.39times10-15 < d/dt In muCs/muB < 0.47times10-15 yr-1.

We describe a new laser system we have developed to probe the ultra-narrow 1S0 harr 3P0 clock transition at 578 nm in neutral ytterbium. The yellow light is produced by sum frequency generation in a periodically poled waveguide. With approximately 100 mW each from a fiber laser and Nd:YAG laser, we produce 10 mW of visible light. Stabilization of the laser to a resonance of a high finesse, environmentally isolated cavity has enabled resolution of spectroscopic features as narrow as 5 Hz.

A stabilized femtosecond frequency comb has ~106 stable optical modes spanning hundreds of terahertz, making it an ideal tool for high-resolution spectroscopy. The frequency comb used in these experiments was generated with an octave-spanning, femtosecond, mode-locked laser based on Ti:sapphire with a repetition rate of ~1 GHz. We demonstrate some features of frequency-comb spectroscopy using experiments involving calcium and cesium.

We perform precision spectroscopy on /sup 27/Al/sup +/ with the aid of a /sup 9/Be/sup +/ ion. Using sympathetic cooling and quantum state transfer, we efficiently interrogate the /sup 1/So /spl rarr/ /sup 3/Pi and /sup 1/So /spl rarr/ /sup 3/Po transitions.

We obtain direct stabilization of the laser offset frequency for a conventional geometry, octave spanning, Kerr-lens modelocked Ti:sapphire laser. Beam characteristics of the continuum are presented.

We detect the carrier-envelope offset frequency of ultrashort optical pulses using quantum interference control of injected photocurrents in low-temperature-grown gallium arsenide. With further improvements to the signal fidelity, this solid-state detection method will enable stabilization of the carrier-envelope offset frequency of femtosecond modelocked laser pulses for optical frequency metrology

We demonstrate quantum interference of injected photocurrents in a semiconductor using a phase stabilized modelocked Ti:sapphire laser. Using this technique we detect the laser offset frequency with a 40 dB signal to noise ratio in a 10 Hz resolution bandwidth.

We present advances in carrier-envelope phase stabilization of mode-locked lasers within the scope of both optical frequency metrology and ultrafast science.

A remarkable synergy has been formed between precision optical frequency metrology and ultrafast laser science. This has resulted in control of the frequency spectrum produced by mode-locked lasers, which consists of a regular “comb” of sharp lines. Such a controlled mode-locked laser is a “femtosecond optical frequency comb generator.” For a sufficiently broad comb, it is straightforward to determine the absolute frequencies of all of the comb lines. This ability has revolutionized optical frequency metrology and synthesis, and it has also led to recent demonstrations of atomic clocks based on optical frequency transitions. In addition, the comb technology is having a strong impact on time-domain applications, including control of the carrier-envelope phase, precision timing synchronization, and synthesis of a single pulse from independent lasers.

The combination of time and frequency domain techniques has enabled the phase stabilization of modelocked lasers, which has impacted optical frequency metrology and phase sensitive time domain experiments.

The recent melding of ultrafast technology with laser stabilization techniques has enabled the stabilization of the carrier-envelope phase. This has impacted optical frequency metrology and optical clocks and promises advances in ultrafast sciences.

We directly stabilize the carrier-envelope phase for a conventional geometry, octave spanning, Kerr-lens mode-locked Ti:sapphire laser. Beam characteristics of the continuum are presented.

We present an optical frequency divider based on a 200 MHz repetition rate Er:fiber mode-locked laser that, when locked to a stable optical frequency reference, generates microwave signals with absolute phase noise that is equal to or better than cryogenic microwave oscillators. At 1 Hz offset from a 10 GHz carrier, the phase noise is below -100 dBc/Hz, limited by the optical reference. For offset frequencies > 10 kHz, the phase noise is shot noise limited at -145 dBc/Hz. An analysis of the contribution of the residual noise from the Er:fiber optical frequency divider is also presented., 4 pages, 3 figures