In general, etching on denim bleaches out the color to produce a lighter or white color on the etched areas. Most types of denim etch well, but you will find that solid-color denim looks better than the variegated type that has white threads running through it.
For this application, galvanometric is the preferred type of laser. This type of laser is available as a laser bridge or standalone type. Laser plotters, which are older technology, can also be used, but you risk damaging the fabric because of the sharpness of the beam.
In addition to etching a logo, name, or shape into denim, it is a great way to create a distressed look. Lasers are often used to add “whiskers” to the natural crease areas of jeans as well as other worn effects. Distressed effects can vary from light etching into the fabric to deep hole penetration, which when combined creates a shredded effect on denim.