Efficiency of thin-film acoustooptic light deflectors for a Gaussian guided optical beam

We have investigated deflection efficiency of thin-film acoustooptic light deflectors for a narrow guided optical beam (GOB). Dependences of the maximum deflection efficiency eta(max) on spreading angle (deltatheta) of such a GOB and that (deltaPhi) of a surface acoustic wave were revealed experimentally and theoretically for He-Ne and GaAlAs double heterostructure (DH) lasers. eta(max) is drastically reduced when deltatheta increases to deltaPhi; and eta(max) increases with increasing deltaPhi for fixed deltatheta. Even for a DH laser having a spectral halfwidth of about 63 A, the spectral distribution scarcely affects eta(max) in this deflector. Some restrictions are pointed out in designing the deflector with higher eta(max) for a narrow GOB.