We stabilized the carrier-envelope phase of the pulses emitted by a femtosecond mode-locked laser by using the powerful tools of frequency-domain laser stabilization. We confirmed control of the pulse-to-pulse carrier-envelope phase using temporal cross correlation. This phase stabilization locks the absolute frequencies emitted by the laser, which we used to perform absolute optical frequency measurements that were directly referenced to a stable microwave clock.

We demonstrate a great simplification in the long-standing problem of measuring optical frequencies in terms of the cesium primary standard. An air-silica microstructure optical fiber broadens the frequency comb of a femtosecond laser to span the optical octave from 1064 to 532 nm, enabling us to measure the 282 THz frequency of an iodine-stabilized Nd:YAG laser directly in terms of the microwave frequency that controls the comb spacing. Additional measurements of established optical frequencies at 633 and 778 nm using the same femtosecond comb confirm the accepted uncertainties for these standards.

Abstract. This paper reviews recent progress on ultrashort pulse generation with erbium-doped fiber ring lasers. The passive mode-locking technique of polarization additive pulse mode-locking (P-APM) is used to generate stable, selfstarting, sub-500 fs pulses at the fundamental repetition rate from a unidirectional fiber ring laser operating in the soliton regime. Saturation of the APM, spectral sideband generation, and intracavity filtering are discussed. Harmonic modelocking of fiber ring lasers with soliton pulse compression is addressed, and stability regions for the solitons are mapped and compared with theoretical predictions. The stretchedpulse laser, which incorporates segments of positive-and negative-dispersion fiber into the P-APM fiber ring, generates shorter (sub-100 fs) pulses with broader bandwidths (> 65 nm) and higher pulse energies (up to 2.7 nJ). We discuss optimization of the net dispersion of the stretched-pulse laser, use of the APM rejection port as the laser output port, and frequency doubling for amplifier seed applications. We also review the analytical theory of the stretched-pulse laser as well as discuss the excellent noise characteristics of both the soliton and stretched-pulse lasers. 42.60F; 42.65; 42.80 Fiber lasers were made possible in the 1960s by the incorporation of trivalent rare-earth ions such as neodymium, erbium, and thulium into glass hosts [1]. Soon thereafter neodymium was incorporated into the cores of fiber waveguides [2,3]. Due to the high efficiency of the Nd +3 ion as a laser, early work focused on Nd +3 -doped silica fiber lasers operating at 1.06 µm [4]. Doping of silica fibers with Er +3 ions was not achieved until the 1980s [5,6]. Since that time Er +3 -doped fiber lasers have received much attention, because the lasing wavelength at 1.55 µm falls within the low-loss window of optical fibers and thus is suitable for optical fiber communications. Rare-earth ions such as Ho +3 [7,8], Tm +3 [9-11], and * Current address: Lucent Technologies/Bell Labs, 791 Holmdel-Keyport Road, Holmdel, NJ, USA * * Current address: NTT Access Network Systems Laboratory, Tokai-mura, Naka-gun, Ibaraki-ken 319-11, Japan Yb +3 [12,13] have also been used as dopants or co-dopants in silica or fluoride fibers, allowing new lasing or pumping wavelengths, and Pr +3 has been incorporated into fluoride fiber, providing emission at 1.3 µm [14,15]. PACS:Among the numerous advantages of fiber lasers are simple doping procedures, low loss, and the possibility of pumping with compact, efficient diodes. The fiber itself provides the waveguide, and the availability of various fiber components minimizes the need for bulk optics and mechanical alignment. Many different cavity configurations can be easily built with fibers and fused-fiber couplers, including linear FabryPerot, ring, and combinations of the two. Enhancement of the fiber nonlinearity due to large signal intensities and long interaction lengths is an additional advantage of fiber lasers that is particularly important for mode-locki...

Three distinct techniques exist for distributing an ultrastable frequency reference over optical fibers. For the distribution of a microwave frequency reference, an amplitude-modulated continuous wave (cw) laser can be used. Over kilometer-scale lengths this approach provides an instability at 1 s of approximately 3 x 10(-14) without stabilization of the fiber-induced noise and approximately 1 x 10(-14) with active noise cancellation. An optical frequency reference can be transferred by directly transmitting a stabilized cw laser over fiber and then disseminated to other optical and microwave regions using an optical frequency comb. This provides an instability at 1 s of 2 x 10(-14) without active noise cancellation and 3 x 10(-15) with active noise cancellation [Recent results reduce the instability at 1 s to 6 x 10(-18).] Finally, microwave and optical frequency references can be simultaneously transmitted using an optical frequency comb, and we expect the optical transfer to be similar in performance to the cw optical frequency transfer. The instability at 1 s for transfer of a microwave frequency reference with the comb is approximately 3 x 10(-14) without active noise cancellation and <7 x 10(-15) with active stabilization. The comb can also distribute a microwave frequency reference with root-mean-square timing jitter below 16 fs integrated over the Nyquist bandwidth of the pulse train (approximately 50 MHz) when high-bandwidth active noise cancellation is employed, which is important for remote synchronization applications.