The investigation of tunable solid-state laser crystal attracted many scientists in the past years. To search new compounds with garnet structure was one of the main fields. YGG:Cr is a laser crystal with prospects

but its spectral properties have not been investigated thoroughly yet.In YGG:Cr

Cr

3+

substituted Ga ions located at slightly trigonal distorted octahedral site. Its

2

E energy level affected by non-octahedral crystal field and spin-orbit couple was splited up into

E

and

2

A

. As shown in the absorption spectrum

the splitting was small

so we used the crystal field parameters of Ok group to fit the energy levels of Cr

3+

. Referring the Tanabe-Sugano energy levels diagram of d

3

electron

the peaks and bands in the absorption spectrum were assigned. The fitting results were in agreement with the experimental data very well. By data fitting

the crystal field parameters

D

q

B

and

C

were obtained. Based on Huang Kun theory

Huang Kun factor

S

and average phonon energy

hω

were derived from the experimental data.