The techniques for fabricating a hollow optical fiber with an inner silver layer and a cyclic olefin polymer (COP) layer have been improved to reduce the surface roughness of these two layers. The loss spectrum was thereby drastically reduced over a wide wavelength range, from visible to near infrared. Optimization of the COP layer thickness resulted in low loss simultaneously at several key laser wavelengths. Infrared hollow fiber with low loss was developed for Er:YAG and Nd:YAG lasers. It can also deliver green and red pilot beams with low loss. Use of this fiber in therapeutic and pilot lasers should prove useful for research and development in laser medicine.