It is shown that simultaneous locking of longitudinal and transverse m
odes is possible in a semiconfocal cavity. A laser with a high repetit
ion rate (10-100 MHz) then emits alternately strongly and weakly diver
ging pulses. A laser operating in this way may be useful in various so
unding and ranging applications. A laser with such locking is a wide-a
perture device with a large volume of the active medium.