60SMS-1-4-M15-26-Ti

The laser beam coupler series 60SMS is designed for compact and long-term stable coupling of singlemode laser radiation into a singlemode or polarization-maintaining fiber. For multimode applications please use the series 60FC-A19.5 fiber couplers.

The features of the coupler type 60SMS include:

Optics
The achromat with focal length 15 mm is designed for coupling multiple wavelengths. It is AR-coated from 420 - 700 nm. It is corrected for spherical aberrations and designed in such a way that it leads to a diffraction-limited spot with an M² < 1.05. Additionally it is corrected for chromatic aberration so that there are certain wavelengths or wavelength ranges where the focal length does not vary significantly. It is not suitable for UHV applications.

High long-term stability
It‘s compact size as well as the high-resolution alignment mechanisms allow for a straight-forward, intuitive coupling procedure.The result is a fiber coupling with high thermal stability, pointing stability, that is vibration and shock-insensitive. Long-term stability tests (see figure on the right) have shown a power stability better than 3 % for a temperature range of 15 - 35 °C.

6 Degrees of freedom*
In order to achieve optimum coupling efficiency the fiber coupler needs to provide certain degrees of freedom. You need to adjust the angle between laser beam and lens/fiber end-face, the z-position of the lens, adjust the polarization axis of the fiber to that of the laser source and center the lens with respect to the laser beam. The fiber coupler provides all degrees of freedom necessary. It has a TILT adjustment, an independent focus adjustment, can be rotated 360°, and allows for lateral adjustment* using e.g the adapter 60A19.5-F.

The TILT adjustment is used to maximize the lateral overlap between the mode field of the fiber and the focussed laser spot using 3 adjustment screws. 3 locking screws are used for fine-adjustment and to lock the position for an optimum mechanical stability.

Independent to the TILT adjustment, the distance between fiber end-face and coupling optics is adjusted by means of an eccentric key. The final focus setting is locked by means of two radially arranged clamping screws. Since the focus adjustment is independant, the z-position of the mode field diameter can be placed much more precisely.

The polarization alignment of the fiber to the polarization axis of the laser source is performed by rotating the laser beam coupler. The separation of the fiber coupler and the adapter necessary for centering is essential to allow for a full 360° freedom of rotation. The coupler has a tight-fit cylinder that can be placed into a 19.5 mm receptacle of a corresponding adapter.

The beam can be centered with respect to the aperture of the coupling optics using e.g. the adapter 60A19.5-F.

Optimum lens performance
The angled polish of connectors of type APC causes the beam to exit in an angle and not parallel to the optical axis of the fiber. This is corrected by the pre-angled mechanical coupling axis of the coupler. that compensates the beam deflection and you can use the lens centrically. This minimizes aberrations simply resulting from a non-ideal beam path through the lens.

Connector Type
The fiber coupler is equipped with a FC-APC type receptacle. Because of the spring-loaded fiber ferrule the fiber coupler has an additional grub screw to increase pointing stability.

Material
The fiber coupler type 60SMS is made from amagnetic titanium. The relative permeability is near 1 (µr = 1.00005) making it almost transparent to magnetic fields. The linear coefficient of thermal expansion is close to that of the optics so that a thermal stability over a larger temperature range can be expected.