Optical thin-film structures exhibiting high reflectivity and a nearly constant negative group-delay dispersion over frequency ranges as broad as 80 THz are presented. This attractive combination makes these coatings well suited for intracavity dispersion control in broadband femtosecond solid-state lasers. We address design issues and the principle of operation of these novel devices.

/pdf/chirped-multilayer-coatings-for-broadband-dispersion-control-44p51swmhb.pdf

Chirped multilayer coatings for broadband dispersion control in femtosecond lasers

The exploitation of soliton-like pulse shaping mechanisms and the optimization of phase dispersion in broadband self-modelocked solid state laser oscillators have led to unprecedented advances in ultrafast laser technology. This paper reviews the basic physical mechanisms governing pulse formation and addresses the requirements for optimum performance of these novel ultrashort pulse laser sources. These considerations together with the demonstration of /spl ap/10 fs pulse generation from a Ti:sapphire laser suggest that a family of solid-state laser oscillators with comparable performance can be developed. >

Ultrabroadband femtosecond lasers

A more exact model is suggested for the description of nonlinear light propagation in fibers. In addition to the previously discussed self-phase modulation, parametric, dispersion, self-steepening, and Raman self-scattering effects, this model also takes into account the Stokes losses associated with the material excitation, the dependence of nonlinear effects on the light frequency, and the frequency dependence of the fiber mode area. The self-steepening effect is taken into account more correctly in comparison with previous models. The effects influence considerably the femtosecond soliton propagation. The model is generalized for the case of various fiber dispersion properties along the fiber length. The possibility of obtaining high-quality pulses of less than 15-fsec duration by compression of fundamental solitons with approximately 100-fsec duration in fibers with slowly decreasing dispersion is shown.

Ultrashort-pulse propagation in optical fibers

We study the evolution of a pulse propagating in a normally dispersive fiber in the presence of Kerr nonlinearity. We review the temporal and spectral impact of optical wave-breaking in the development of a continuum. The impact of linear losses or gain is also investigated.

/pdf/beneficial-impact-of-wave-breaking-for-coherent-continuum-2q8h5rvgbu.pdf

Beneficial impact of wave-breaking for coherent continuum formation in normally dispersive nonlinear fibers

By using the novel approach for pulse compression that combines spectral broadening in hollow-core fiber (HCF) with linear propagation in fused silica (FS), we generate 1.6 cycle 0.24 mJ laser pulses at 1.8 μm wavelength with a repetition rate of 1 kHz. These pulses are obtained with a white light seeded optical parametric amplifier (OPA) and shown to be passively carrier envelope phase (CEP) stable.

CEP stable 1.6 cycle laser pulses at 1.8 μm

Using computer simulations, we examine the effects of higher-order dispersive and nonlinear propagation processes on the spectral and time development of ultrashort, high-intensity pulses propagating in single-mode optical fibers having normal dispersion. Our results indicate that both the cubic-dispersion term and the shock term of the nonlinear Schrodinger equation contribute to asymmetry in the pulse power spectrum and cause highly nonlinear chirp.

Evolution of femtosecond pulses in single-mode fibers having higher-order nonlinearity and dispersion.

Intensity-dependent spectra of pulses propagating in optical fibers

We present an analytical treatment of the reflection of femtosecond pulses from broad-band multiple-layer dielectric mirrors. In particular, closed-form expressions are given for the reflected pulse amplitude which includes the dispersive effect of the cubic phase term. It is shown that this term is still insufficient to accurately describe certain experimental results obtained with 20-fs optical pulses. We introduce an alternative technique which describes the phase branches analytically and yields accurate closed-form expressions for the reflected pulse amplitude in terms of complementary error functions having real or complex arguments.

Reflection of femtosecond optical pulses from multiple-layer dielectric mirrors--Analysis

Using computer simulations, we examine the effects of higher-order dispersive and nonlinear propagation processes on the spectral development of ultrashort, high-intensity pulses propagating in normally-dispersive fibers. Both the cubic dispersion term and the “shock” term of the nonlinear Schrodinger equation each contribute to asymmetry in the pulse power spectrum. This asymmetry depends on the particular combination of these higher-order effects. Our results indicate that the two effects, cubic dispersion and the shock term, can contribute significantly toward explaining recent compression experiments when both are incorporated into the nonlinear Schrodinger equation.

https://www.osapublishing.org/viewmedia.cfm?uri=CLEO-1987-TUK42&seq=0

D. N. Christodoulides

Papers

Evolution of femtosecond pulses in single-mode fibers having higher-order nonlinearity and dispersion.

Intensity-dependent spectra of pulses propagating in optical fibers

Reflection of femtosecond optical pulses from multiple-layer dielectric mirrors--Analysis

Intensity-dependent spectra of pulses propagating in optical fibers