**2.2 Laser processing protocol of photosensitive materials**

For a reproducible fabrication of a required design a good control of processing protocol is necessary. The main processing steps are: the substrate preparation; deposition of the photosensitive material; laser irradiation; development and final curing of the polymerized structures.

#### **2.2.1 Substrate preparation for photoresist deposition**

A critical step is the initial treatment of the substrate in order to provide a good adhesion of the polymerized structure. The frequently used treatments are cleaning by reactive plasma etching, chemical corrosion, or a simple ultrasonic bath in solvents followed by thermal dehumidification, depending on the substrate nature (silicon wafer, glass, fused silica). A promoter film deposition is sometime a good solution to increase adhesion, especially in the case of glass substrate with reduced adherence. Producing photoresists with enhanced adhesion is also desirable, since the treatment of the substrate is simplified. All the following processing steps are preferable to deploy in a controlled environment since the dust can easily stick to the photoresist film, compromising the final geometry.
