The present invention relates to a laser device, and more particularly to an optical fiber laser device used for a pulse laser conducting device. 
As a therapy in the body cavity, there is known a therapy using a laser beam which is called photodynamic therapy.  This therapy uses a laser device, particularly a pulse laser conducting device, to perform a treatment by applying a laser optical energy compressed in a pulse state into the body cavity through an optical fiber.  In this therapy, however, the optical energy partly becomes a shock wave, and the shock wave causes splashing of tissue fluid.  The tissue fluid becomes firmly adhered and bonded to a lens at an extreme end of the optical fiber and contaminates the surface of the lens.  This poses a problem in that it is very difficult to remove the contamination on the lens. 
FIG.  1 shows the construction of an extreme end portion of a conventional optical fiber laser device used for laser therapy such as photodynamic therapy.  The conventional optical fiber laser device comprises an optical fiber 1, a base 2 for housing therein a lens, a cylindrical GRIN lens 3, and a pawl 4 for preventing the GRIN lens from falling out of the base 2, the pawl constituting a part of the base 2. 
In the process of the laser therapy such as the photodynamic therapy, it is often necessary to uniformly irradiate a laser beam on the affected part in the body cavity.  In this case, it is necessary to provide an adequate lens on the extreme end of the optical fiber.  Conventionally, a cylindrical GRIN Lens 3 known as a "SELFOC" lens is used, which is encased in the base 2 at the extreme end portion of the optical fiber 1 as shown in FIG.  1. 
However, since in the above-described conventional construction, the pawl 4 for preventing lens 3 from falling out is present, the baked contamination, on the surface of the lens cannot be cleaned and wiped off.  In fact, even if the lens surface is cleaned immediately after being contaminated by a method such as ultrasonic cleaning, the contamination can hardly be removed.