The cw modeless laser: spectral control, performance data and build-up dynamics

Abstract

The modeless laser is a device which provides intense broadband light fields, but without the usual frequency domain mode structure of conventional lasers. This new feature for cw lasers is due to the introduction of an additional parameter: the intracavity frequency shift, which prevents constructive interference of the circulating field. This intra-cavity frequency shift, in combination with frequency-selective elements, determines the bandwidth, output power and thereby the peak spectral energy density in a unique way. We report on bandwidth control and the associated performance of the laser using various intra-cavity etalon passbands and shift frequencies. The build-up dynamics are also shown to underline the interplay of shift frequency and passband width. A minimum bandwidth of 1 GHz fwhm of the modeless laser field is achieved with a maximum spectral power density of 150 μW/MHz. This is an interesting bandwidth and spectral density for exciting an entire Doppler ensemble or pumping many narrowly spaced resonance lines. The intensities are sufficient to saturate a typical transition.