Diffractive optics opens unique possibilities to affect only one wavelength. In multi-wavelength light beams the dual wavelength beam combiners are diffractive optical elements used to combine two incident beams with different wavelengths into the same focal point. In order to gain a super imposed spot on a required plane one just have to place a transparent diffractive optical element in the path of the laser beam towards the spot. No doublets are used anymore, only one hybrid diffractive element with microrelief on the plane side. The durability of diffractive beam combiner is far better then two lens system. Integral light transmittance of diffractive dual wavelength element (can reach 98%) exceeds any on-axis reflective systems.
 

	Performance of regular ZnSe lens in dual-wavelength beam of CO2 and HeNe lasers
	Performance of diffractive-refractive ZnSe lens in dual-wavelength beam of CO2 and HeNe lasers