Dan Provenzano

Improved laser modulation response by frequency modulation to amplitude modulation conversion in transmission through a fiber grating

We have demonstrated that transmission through a fiber grating can increase the system response of a directly modulated semiconductor laser by over 7 dB at all modulation frequencies up to 25 GHz. When combined with dispersive optical fiber, the grating produced a system response that was larger, flatter, and had a larger bandwidth, providing a frequency-domain demonstration of dispersion compensation through an unchirped grating. The effect can be understood as frequency modulation to amplitude modulation conversion by the grating, and was accurately predicted by a Fourier domain analysis of the laser signal and grating.

Effect of transmission through fiber gratings on semiconductor laser intensity noise

The effect of transmission through a fiber Bragg grating on the relative intensity noise of semiconductor laser light is investigated. We first present a model of the grating as a linear frequency discriminator that exchanges correlated power between frequency noise and intensity noise caused by spontaneous emission. This correctly explains observed increases in intensity noise of up to 30 dB at low frequencies, obeying an inverse-square frequency dependence. Next, we show that there exist conditions under which a grating can reduce intensity noise and that these are determined by the phase relationship between correlated intensity and frequency fluctuations. Finally, we demonstrate a 2 dB reduction of intensity noise at frequencies up to 15 GHz, and present a numerical calculation based on the complex transmittance of the grating that correctly describes the effect of grating dispersion.

Effect of many weak side modes on relative intensity noise of distributed feedback semiconductor lasers

An increase of the relative intensity noise of nearly single-mode distributed feedback lasers with respect to that predicted by single-mode theory after propagation in dispersive fiber at frequencies up to 5 Ghz has been measured. A simplified multimode theory is presented which explains the increase in noise.

Generation of amplitude-squeezed light from a room-temperature Fabry-Perot semiconductor laser

Amplitude-squeezed light with intensity fluctuations 29% below the standard quantum limit (SQL) is produced from a pump-suppressed room-temperature semiconductor laser, corresponding to 41% below the SQL after correction for detection efficiency. Excess noise, which degrades the observed squeezing, appears to be associated with the presence of weak longitudinal side modes.

Double phase mask fabrication of fiber Bragg gratings

The development of fiber Bragg gratings has enabled fabrication of a variety of different Bragg grating devices that were not possible previously, such as dispersion compensators and band-rejection filters.

Effect of many weak side modes on relative intensity noise of distributed feedback semiconductor lasers after dispersive propagation

The performance of a lightwave communication system can be affected by the lasers relative intensity noise (RIN) and mode partition noise (MPN). In addition, measurements of RIN after propagation in fiber can be used to obtain several important intrinsic laser parameters. Therefore an accurate and simple model of RIN after dispersive propagation is necessary. We report here an effect of MPN that can affect RIN in low-noise distributed feedback (DFB) lasers even with side-mode suppression ratios higher than 40 dB and at frequencies up to 5 GHz, and which cannot be explained by previous single-mode models. We present a multimode theory of RIN after propagation in fiber in which the effect of FM to AM conversion in the fiber has been included via a generalization of the transfer function approach to the multimode case. The additional parameters that are needed in this multimode model are experimentally obtained from a measurement of the optical spectrum. This allows us to get theoretical fits that agree well with experimental measurements of RIN.