Lasers (FS)

In addition to the standard light sources described elsewhere in the manual, OghmaNano also includes a special class of light sources called femtosecond lasers. These lasers differ from normal light sources in that they do not have a broad spectrum; instead, they are defined by a single spectral value, making them extremely narrow in wavelength. As shown in the ??, femtosecond lasers can be accessed from the Optical ribbon.

Femtosecond lasers are configured through the editor window (??). Their key parameters include the laser wavelength, spot size in both x and y, the energy per pulse, the pulse length, and an efficiency factor for photons. This efficiency term provides a way to account for losses at interfaces, such as reflection. In the example shown, the configuration is for a green laser with a wavelength of 520 nm, but these values can be adjusted as required.

These lasers are designed to represent femtosecond sources such as Nd:YAG-type systems used in ultrafast measurements of perovskites, organic semiconductors, and other materials. They are special in that they emit only for very short durations, often far shorter than the time step of the simulation mesh. For example, if the simulation time step is one nanosecond, the laser might emit for only a single femtosecond within that interval. As a result, the power delivered is sharply defined, which is particularly important for modelling transient phenomena such as photocurrent measurements. Femtosecond lasers are therefore a specialised feature within OghmaNano, distinct from normal light sources, and are primarily intended for use in optoelectronic transient device simulations.