Polarization independent optical isolator

A polarization independent optical isolator comprising:

• (a) a first birefringent plate for separating a signal ray passing therethrough into first and second rays having first and second orthogonal polarizations wherein the first ray of the first orthogonal polarization experiences a first spatial displacement as it passes through said first birefringent plate in a first transmitting direction;
• (b) non-reciprocal rotating means for rotating said first and second rays about .pi./4+n .pi./2 in a first rotational direction of said first transmitting direction, wherein n is an integer;
• (c) a second birefringent plate for combining said first and second rays from said non-reciprocal rotating means to produce a combined ray wherein the first ray experiences a second spatial displacement as it passes through said second birefringent plate in said first transmitting direction, a distance of said first spatial displacement being substantially equal and opposite in directing to that of said second spatial displacement;
• (d) first reciprocal rotating means provided between said first and second birefringent plates so as to intercept said first and second rays for rotating said first and second rays about .pi./4 in a second rotational direction of said first transmitting direction that is opposite to said first rotational direction of said first transmitting direction;
• (e) reflection means for redirecting said combined ray in a second transmitting direction into said second birefringent plate, said second birefringent plate separating said redirected combined ray into third and fourth rays, said non-reciprocal rotating means rotating said third and fourth rays about .pi./4+n .pi./2 in a first rotational direction of said second transmitting direction;
• and
• (f) second reciprocal rotating means provided between said first and second birefringent plates so as to intercept said third and fourth rays for rotating said third and fourth rays about .pi./4 in a second rotational direction of said second transmitting direction that is opposite to said first rotational direction of said second transmitting direction;
• wherein said first birefringent plate combines said third and fourth rays from said non-reciprocal rotating means to produce a combined output ray;
• and
• wherein said first reciprocal rotating means is located adjacent to said second reciprocal rotating means.