This dataset contains the files obtained from the optical spectrum analyzer, by inserting a multimodal interference filter (MMIF) coated with graphite oxide into the ring-shaped laser cavity. The data, according to the file name, is divided into three parts. In one dataset are the spectrum of the cavity, at different pump powers, before inserting the MMIF. The other data set has the spectrum at different pump powers, with the MMIF without graphite oxide coating in the laser cavity. The last data set contains the spectrum at different pump powers, with the MMIF coated with graphite oxide inside the laser cavity.