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Chapter 2
Diode laser overview: how it is done and how to manage it
the laser emission by pressing a button on the handpiece or by means of a foot pedal. A specific connection is therefore available, depending on the manufacturer’s choices. The physical connection with the unit is, however, absent in the case of systems with wireless pedals. Some units have an auxiliary connection that can be used to connect a remote interlock type control. Recently some devices have been equipped with auxiliary connections (serial/USB/MICRO-USB) to allow easier maintenance of the system by qualified personnel and, moreover, to allow the operator to update the software with new clinical programs and customized settings (! 2.13). Inside the device is the active medium, the “beating heart” of the entire system. Since the present dissertation is focused on the diode laser, the active medium consists of a semiconductor. The semiconductor is made up of several layers of materials of different nature (generally Ga, As, Al). The diode is connected to a specific collimator support, in turn interconnected with an optical fiber which has the function of bringing the beam to the interconnection device with the outside.
Connection between main unit and means of transport-conduction The manufacturer usually interfaces the medical laser to the conduction system by applying a special connector on the proximal side of the latter. Through the connection interface, the beam emitted by the main unit is conveyed within the conduction medium (optical fibers, cords, articulated arms, etc.). Sometimes the main device has a closed/“proprietary” connection, that is customized by the manufacturer; in this last case, the operator is bound in choosing only the components and accessories produced by the parent company, without the possibility of contacting third parties. Sometimes, there is not even the possibility for the user to be able to change the means of operation. In the latter case, it is impossible to use optical fibers, biostimulation handpieces and other accessories, resulting in a severely limited clinical operation. More performing devices generally adopt “open” or universal connections, where the user is given the op-
! 2.14 SMA 905 connection. An SMA 905 universal female connection is present on the main laser unit. Note the black silicone hermetic protection device (Pocket Laser®, 88Dent, Pero, MI, Italy).
portunity to intervene on the connection between the main device and the means of conduction, so as to be able to choose the most appropriate one according to specific needs. Compared to the standard ST and FC connectors, the SMA type appears to be the most frequently used solution in medical systems, even if no longer used in the telecommunications sector.3 In this type of connector it is possible to integrate a mechanical or electronic interlocking device for the authorized use of medical lasers and ocular safety. The SMA 905 connection, located at the level of the main unit (female), is a universal type connection capable of hosting universal male SMA 905 connectors. The coupling of the two interfaces is guaranteed by a screw assembly (! 2.14). Once the connector is inserted, it is able to maintain its position with extreme precision, an essential requirement for the correct conduction of the laser beam. It is essential to preserve the integrity of the connection area, protecting it with special seals or hermetic closing devices. The perfect coupling between the connectors allows the laser beam to be transmitted without alterations and power losses. The possible presence of impurities or residues in the interface structure is potentially capable of altering the conduction mechanism of the light beam. The occurrence of unwanted damage to this delicate interface is also possible. Damage can be reversible or irreversible and still require the intervention of a specialized technician.
