There are many performance data that specify a complex unit like MOG. We have concentrated on ergonomics, but always with the ultimate laser linewidth in mind. The diode injection current noise is so low that in almost all cases, the laser performance is determined by the optical characteristics of the external cavity, not the MOGbox.

Current noise

The curve above shows the diode injection current noise (or lack thereof). Measured at 50mA into 50ohms (orange trace) and zero current (blue trace). The current noise level is well below -145dBm for nearly all of the spectrum (at 1Hz RBW).

Frequency noise

Here we show typical feedback error signal noise spectra with a MOGbox controller and ECD-003 monoblock laser. The spectra are relatively free of mechanical resonances.

Linewidth

The figure below shows a self-heterodyne beatnote for a single diode laser, locked to a rubidium transition. The beatnote width was roughly 80kHz (FWHM), 35kHz (rms). Our linewidth measurements are described in Linewidths below 100 kHz with external cavity diode lasers, Appl. Opt. 48 6961-6966 (2009). The self-heterodyne technique is described in Electron. Lett. 16 630-631 (1980).

In another experiment, we demonstrated a wide-bandwidth frequency locking technique based on an electromagnetically induced transparency (EIT) using FM sideband locking (essentially Pound-Drever-Hall). The figure below shows the beatnote frequency with two lasers locked to transitions in Rb87, with different hyperfine ground states separated by 6.8GHz. One MOG was locked to a saturated absorption peak, the other to the EIT resonance. The beatnote, which is a measure of the relative frequency stability, has a width of 4kHz for a 22.5s average, and less than 1kHz for a single sweep of 0.2s. The work was published in Appl. Phys. Lett.90 171120 (2007).

Scan range

The scan range available depends very much on the mechanical and optical design of your laser. Using a standard laser diode for cd-rom writing applications (Sharp GH0781JA2C or Roithner Lasertechnik ADL-78901TX), without special coatings, and a low-efficiency 1800l/mm grating, scans of about 1GHz are typical in a Littrow configuration. Increased scan range is possible by careful design of the pivot point of the grating, so that the frequency change due to the change in cavity length closely matches the frequency change due to the change in grating angle. See for example our recent paper Appl. Opt., 48 6692-6700 (2010).

We can instead ramp the diode injection current and cavity length (piezo) together. With standard uncoated diode, low-feedback grating and Littrow configuration, we can scan up to 30GHz without mode-hops. The figue below shows a 10GHz wide saturated absorption spectrum for the 780nm rubidium transition, with both naturally occurring isotopes, approximately 10GHz. The figure below shows the saturated absorption and the MOG error signal with a standard MOGbox.