Volume 61, Number 3, 2011¸ 3 Z 4, pp. 268∼271
New Physics: Sae Mulli (The Korean Physical Society), DOI: 10.3938/NPSM.61.268
°
Æ W ¥ Ö כ ; c 8 ýA 0 ù m É Ò ×c Ü R 7 _T $ [° Ë Ñ8 ý M 2 ß Ã Å
ç
¡ ¬ £
ô
Çz @ / < Æ § F g Ó ü t o < Æõ , @ / 306-791 (2011¸ 1 Z 4 18{ 9 ~ Ã Î6 £ §, 2011¸ 3 Z 4 8{ 9 > F S X & ñ )
· û
ª É r E $ Ý ¼_ Ã º Y Us $ F g _ M
2 \ p u H % ò ¾ Ó` ¦ ì r$ 3 ô Ç . $ , · û ª É r E $ Ý ¼\ _ K | 9 5 Å q
)
a Y Us $ F g _ 4 Ð& ñ ) a 1 l x < ÊÃ º\ ¦ ½ ¨ô Ç . 4 Ð& ñ ) a 1 l x < ÊÃ º\ H K " f Y Us $ F g _ M
2
\
¦ à ºu > í ß ô Ç . { 9 F g _ ì ø Í â s ß ¼ , E $ Ý ¼_ í& h o  ú ª | 9 à º2 ¤ M
2 / å L y 7 £ x
< Ê` ¦ Ð# ï r . : rë H \ Å Ò# Q 4 Ð& ñ ) a 1 l x < ÊÃ º H · û ª É r E $ Ý ¼\ _ K " f | 9 5 Å q ) a Y Us $ F g _ M
x2
\ ¦ & ñ H X < 6 x| ¨ c à º e .
Ù þ
d # Q: 4 ¤ è& h , Ä ºÛ ¼ F g , ½ ¨ Ã º , M
2
M 2 Factor of a Laser Beam Focused by a Thin Lens
Soo Chang ∗
Department of Physics, Hannam University, Taejon 306-791 (Received 18 January 2011 : accepted 8 March 2011)
We analyze the degradation in the M
2factor of a laser beam caused by the aberration of a thin lens. First, we formulate the fourth-order correction to a paraxial Gaussian beam focused by a thin lens. Then, we numerically evaluate the M
2factor of the fourth-order corrected beam propagating through a thin lens. We show that the M
x2factor increases rapidly either by increasing the incident beam radius or by decreasing the focal length of the lens. The fourth-order corrected wave function given here can be useful in determining the M
2factor of a laser beam focused by a thin lens.
PACS numbers: 42.30.Va
Keywords: Complex source point, Gaussian beam, Spherical aberration, M
2factor
I. " e  ] Ø
' ½ ¨ [1]\ " f Ä ºo H Ä ºÛ ¼+ þ A Y Us $ F g s H» ¡ ¤
% ò
% i \ " f 4 ¤ èà º & h F g " é ¶ \ " f : r ½ ¨ ü < 1 p x s 9 [2], ¦ Ð& ñ ½ Ó` ¦ ¸¿ º í < Êr v 4 ¤ è& h ½ ¨ ü <
{ 9
u ô Ç [3] H z ´\ H K " f é ß { 9 F g < Æ ` ¦ t H 4
¤ è& h ½ ¨ _ õ & ñ ` ¦ á ÔY U3 A q-v Ø Ô ñá Ô r] X & h ì
r [4] Ü ¼ Ð l Õ ü t ô Ç Ê ê, F g F g < Æ& h H \ ¦ : x K " f 4 Ð
&
ñ ½ Ós í < Ê ) a Ä ºÛ ¼ F g _ 1 l x < ÊÃ º` ¦ Ä » ¸ ¦, M 2
∗