% i . Y Us $ s ¸× ¼_ * 3 i ç Ø ¦§ 4 s 22.9 W{ 9 M : 3 W_ 1064 nm-Nd:YAG Y Us $ _ Ø ¦§ 4 ` ¦ % 3 % 3 Ü

(1)

/

B N l \ ¦ s 1 p q B | 9 ? /\ " f_ * 3 i ç F g \ _ ô Ç \ P E $ Ý ¼ ´ òõ \ ¦ ¦ 9 # ½ ¨$ í ¦ Õ ª Ø ¦§ 4 : £ ¤$ í ` ¦ 8 £ ¤& ñ

% i . Y Us $ s ¸× ¼_ * 3 i ç Ø ¦§ 4 s 22.9 W{ 9 M : 3 W_ 1064 nm-Nd:YAG Y Us $ _ Ø ¦§ 4 ` ¦ % 3 % 3 Ü

¼ 9, l Ö ¦ l ´ òÖ ¦ É r 13.4 % Ð 8 £ ¤& ñ ÷ &% 3 . ¢ ¸ô Ç q + þ A & ñ KTP(potassium titanyl phosphate)\ ¦ /

B N l ? /Â Ò\ ¶ ú { 9 ô Ç ? /Â Ò/ B N l Å Ò Ã º C ~ ½ Ód Ü ¼ Ð * 3 i ç Ø ¦§ 4 s 10.6 W{ 9 M :, 130 mW_ î ß & ñ

)

a 0 l qÒ oY Us $ \ ¦ % 3 ` ¦ Ã º e % 3 . s M : 0 l qÒ oY Us $ _ c | 9 p ' M

²

= 1.90, c µ 1 Ïí ß y θ = 9.95 mrad Ü ¼ Ð 8 £ ¤& ñ ÷ &% 3 .

PACS numbers: 42.60.Pk, 42.65.Ky

Keywords: Nd:YAG/KTP 0 l qÒ oY Us $ , \ P E $ Ý ¼ ´ òõ , q + þ A & ñ , ? /Â Ò/ B N l Å Ò Ã º C

I. " e Â ] Ø

s ¸× ¼ Y Us $ H ¦^ Y Us $ _ * 3 i ç F g " é ¶ Ü ¼ Ð 6 x

÷

& " f Ð ¦ ´ òÖ ¦& h / B N l [ O > \ ¦ 0 p x > Ù þ ¡

. ¦Ø ¦§ 4 s ¸× ¼ Y Us $ H l > r _ s : r Y Us

$

\ ¦ @ / K W 1 ¸n ¶ o u(Nd) > \ P ¦^ Y Us $ _ * 3 i ç F g

"

é

¶ Ü ¼ Ð 6 x ÷ & " f ? /Â Ò/ B N l \ ¦ s 6 x ô Ç Å Ò Ã º C ~ ½ Ó d

[1]\ _ K 3 W & ñ ¸\ K { © ÷ & H 5 Å q µ 1 Ï 0 l qÒ o Y Us

$

\ ¦ % 3 l ¸ Ù þ ¡ [2,3]. ¢ ¸ þ j H \ H 946 nm\ ¦ 1 l x Ã º C

r ' õ AÒ oY Us $ \ ' a ô Ç ½ ¨\ " f 473 nm_ ©

\

" f 1.25 W [4], 457 nm\ " f H 4.6 W [5] _ ¦Ø ¦§ 4 ` ¦

%

3 # Q · p כ Ü ¼ Ð Ð ¦÷ &% 3 . s Qô Ç ¦Ø ¦§ 4 ¦^ Y Us $

H * 3 i ç s s À Ò# Qt H 1 l x î ß s 1 p q B | 9 \ " f H * 3 i ç F g \ _

ô Ç f ¨ Ã º { 9 # Q > ÷ & 9, Y Us $ Ø ¦§ 4 õ / B N l < H z

´` ¦ ] jü @ô Ç Qt H \ P Ð ¨ 8 ) a . ¨ 8 ) a \ P É r Í ty s

s À Ò# Qt H B | 9 ³ ð Ü ¼ Ð S X í ß ÷ & ¦, s M : B | 9 ? /Â Ò

\

" f H Ô ¦ç H{ 9 ô Ç : r ¸ì r í Ò q tl > ) a . s : r ¸ì r

í_ q ç H| 9 $ í É r B | 9 _ Ï ã J] X Ò ¦ õ \ P Ø ½ Ó` ¦ / B N ç ß & h Ü ¼ Ð

Ø Ô> ë ß [ þ t # Q \ P E $ Ý ¼(thermal lens) & ³ © [6]s \ P 4 ¤ Ï

ã J] X (thermal birefringence) & ³ © [7] 1 p x` ¦ { 9 Ü ¼ . ¢ ¸ ô

Ç / B N l ? /Â Ò_ ¸× ¼ ß ¼l _ o H s 1 p q B | 9 s q

+ þ A & ñ \ " f_ ¸× ¼ & ñ ½ + Ë(mode matching)\ % ò ¾ Ó` ¦ º

¡

§ É r Ó ü t : r, / B N l _ p èô Ç U ´s o\ Ø ¦§ 4 s y

>

½ + É Ã º e [8]. s ü < ° ú É r & ³ © É r # l F g _ [ jl

∗

E-mail: [email protected]

7 £ x ½ + ÉÃ º2 ¤ 8¹ ¡ ¤ Ì º§ Â K t 9, " f ¦Ø ¦§ 4 ] j2 ¦ ¸

(Second Harmonic Generation, SHG)\ ¦ % 3 H X < e # Q Û

¦ # Q ½ + É × æ כ ¹ô Ç õ ] j ÷ & ¦ e .

\ P

% ò ¾ Ó` ¦ × ¦ s l 0 Aô Ç @ /³ ð& h \ V Ð H Ð © 6 x E $ Ý ¼

\

¦ ¶ ú { 9 [9], λ/4-ó ø Í` ¦ s 6 x ô Ç \ P 4 ¤Ï ã J] X & ³ © _ Ð

© [10] Õ ªo ¦ Nd

³⁺

' ÷ &t · ú § É r YAG\ ¦ Nd:YAG

& ñ ª A á ¤ \ · ¡ # Å Ò H 1 p x [4] ª ô Ç r ¸ s À Ò# Qt ¦ e

.

: r ½ ¨\ " f H s ¸× ¼ Y Us $ Ð 7 á x* 3 i ç ÷ & H - + þ

A Nd:YAG Y Us $ / B N l \ ¦ [ O > ¦ ½ ¨ \ P E $ Ý ¼ ´ ò õ

(spherical thermal lens effect)\ ¦ ¦ 9ô Ç ABCD

' § > =(transfer matrix)` ¦ s 6 x K s 1 p q B | 9 õ q + þ A

&

ñ (nonlinear crystal)\ " f_ c ß ¼l \ ¦ > í ß K 4 § Ü ¼ Ð+

\ P

E $ Ý ¼ ´ òõ c ¸× ¼ o\ p u H % ò ¾ Ó` ¦ · ú Ð ¤ Ü

¼ 9, \ P E $ Ý ¼ ´ òõ \ Ð W = y ô Ç / B N l \ ¦ ½ ¨$ í

¦ % i . s ü < ° ú É r / B N l ½ ¨ ¸\ " f l : r (1064 nm) _ Ø ¦§ 4 õ l Ö ¦ l ´ òÖ ¦(slope efficiency)` ¦ 8 £ ¤& ñ

%

i Ü ¼ 9, ? /Â Ò/ B N l 1 l x Ã º C (intracavity frequency doubling) ~ ½ Ód ` ¦ s 6 x # 532 nm_ 0 l qÒ o Y Us $ \ ¦ % 3

%

3 . s M : * 3 i ç F g _ [ jl \ É r 0 l qÒ o Y Us $ _ Ø ¦§ 4 , c

| 9 p ' (beam quality parameter, M

²

) x 9 µ 1 Ïí ß y

(divergence angle)` ¦ 8 £ ¤& ñ % i .

-554-

(2)

Fig. 1. Setup of the LD pumped Nd:YAG laser : D is the distance between M

₁

and L of the collimated arm, and x is the distance between L and M

₃

of the focusing arm.

II. «à Ã ÅM º

Fig. 1 \ H Y Us $ s ¸× ¼ Ð * 3 i ç H Nd:YAG Y U s

$ _ / B N l ½ ¨ ¸\ ¦ ? /% 3 . ï# Q t 2 £ § s 400 µm,

>

h½ ¨Ã º(numerical aperture, NA) 0.22 F g$ 3 Ä »

½

+ Ë ) a s ¸× ¼ Y Us $ (fiber coupled LD, Limo Laser Sys- tem, 808 nm)\ ¦ q ½ ¨ E $ Ý ¼ ¸½ + Ë(aspheric lens pair, f = 11.0 mm, NA = 0.25, AR coated at 600 ∼ 1050 nm)` ¦ :

x K s 1 p q B | 9 Ð | 9 5 Å q r ( . Nd

³⁺

1.1 at.% ' ) a f

â 3 mm, U ´s 5 mm s 1 p q B | 9 Nd:YAG & ñ É r * 3 i ç

(M

1

) s 808 nm\ @ /K ¦È Òõ ÷ & ¦ 1064 nm x 9 532 nm \ @ /K " f H ¦ì ø Í ÷ & ¸2 ¤ ïh A÷ &% 3 Ü ¼ 9, É r É r 1064 nm \ @ /K Á ºì ø Í ÷ & ¸2 ¤ ïh A % i . 45

^◦

Ð , # Q

¨ î Ö ¦ M

2

H 1064 nm \ @ /K ¦ì ø Í , 532 nm\

@

/K 95 % s © È Òõ ÷ & ¸2 ¤ s Ò o ïh A % i . E $ Ý ¼ L É r 1064 nm ü < 532 nm_ © ¸¿ º Á ºì ø Í ïh Aô Ç ^ ¦2 ¤-¨ î

E $ Ý ¼ Ð í& h o 60 mms . 1064 nm\ @ /K 2

% _ È Òõ Ö ¦` ¦ Ø ¦§ 4 Ö ¦(M

3

)` ¦ 6 x # l : r _ Ø

¦§ 4 ` ¦ Molectron _ Ø ¦§ 4 > (Power Max 5100, probe : PM10) Ð S X % i . s M : s 1 p q B | 9 É r # l F g _ f ¨ Ã º

Ð K µ 1 ÏÒ q t ) a \ P s ´ òÖ ¦& h Ü ¼ Ð K è | ¨ c Ã º e ¸2 ¤ ´ o u

í{ 9 Ð y ø ß 6 £ § · ú À Òp ³ o u f . Ë 8\ ¦& ñ r & , ½ ` ¦ s 6 x K

Í ty r ( . s H \ P è \ ¦ s 6 x ô Ç ~ ½ Ód s Ã ºÍ t d

Ð Õ ª t ´ òÖ ¦& h s t H · ú §Ü ¼ , / B N l _ U ´s

U

´t · ú § É r ' a > Ð Â Ò1 p q s 2 [ô Ç ~ ½ Ód s .

M. E. Innocenzi 1 p x _ õ [11]\ Ø Ô , s 1 p q B | 9 \

"

f µ 1 ÏÒ q t÷ & H \ P E $ Ý ¼ ´ òõ \ _ ô Ç Ä »´ ò í& h o H f

th

= πK

_c

w

²_p

P

ph

(dn/dT ) ( 1

1 − exp(−αl) ) (1)

) a .

Fig. 2. Results of the numerical model : (a) length of the collimated arm D = 65 mm, (b) D = 85 mm, (c) D

= 105 mm. w and w

₀

are the mode of radii at M

₁

and M

3

, respectively, as a function of the thermal lens length f

th

.

#

l " f w

^p

H * 3 i ç F g _ c ì ø Í â , P

ph

H * 3 i ç F g _ [ j l

, K

c

, α, Õ ªo ¦ l É r y y s 1 p q B | 9 _ \ P ¸ ¸, f ¨ Ã º

>

Ã º x 9 U ´s s 9, dn/dT É r : r ¸\ É r Ï ã J] X Ò ¦ _ o

\

¦ · p . > í ß \ 6 x ) a K

_c

= 0.13 W/(cm K), w

_p

= 450 µm, dn/dT = 7.3 × 10

⁻⁶

K

⁻¹

, α = 4.1 cm

⁻¹

, l =

(3)

Nd:YAG laser(cavity length = 145 mm).

Fig. 4. Output power of the fundamental beam(1064 nm) versus input power.

5.0 mm s 9, P

th

= 1.48 W, 6.4 W, 10.6 W, 22.9 W, Õ ª o

¦ 30 W{ 9 M : f

th

H y y 87.9 cm, 20.3 cm, 12.3 cm, 5.7 cm, Õ ªo ¦ 4.3 cm\ ¦ % 3 ` ¦ Ã º e % 3 .

s

ç H{ 9 t · ú § É r : r ¸ì r í Ð l ÷ & H B | 9 ? /Â Ò

\

" f_ Ï ã J] X Ò ¦ õ \ P Ø ½ Ó 1 p x _ 4 ¤ ¸ ú ô Ç ë H ] j\ ¦ · û ª É r ½ ¨ E $

Ý ¼ Ð H r & ABCD ' § > = [12]` ¦ s 6 x K M

1

õ M

3

\ " f_ c ß ¼l \ ¦ > í ß Ù þ ¡ . Lõ M

³

s _ o o x \ É r M

1

õ M

³

\ " f_ c ß ¼l \ ¦ y y wü < w

⁰

% i

` ¦ M :, d (1)_ > í ß õ ü < q §½ + Éë ß ô Ç \ P E $ Ý ¼ ´ òõ

\

_ ô Ç í& h o \ ¦ 40 mm, 100 mm, 400 mm, Õ ªo ¦ 1000 mm Ð Ë ¨# Q Ð ¤ . ¢ ¸ô Ç, M

₁

õ L s _ o D\ ¦ or ( Ü ¼ 9 D = 65 mm, 85 mm x 9 105 mm\ @ / ô

Ç > í ß õ \ ¦ Fig. 2 _ (a), (b) x 9 (c)\ y y ? /% 3

.

ë

ß E $ Ý ¼_ í& h o (f = 60 mm) 7 £ ¤, x = f \ " f z ´+ « >

`

¦ Ã º' ô Ç , Fig. 2 (c)_ â Ä º f

^th

= 40 mm{ 9 M : / B N

l î ß & ñ ¸| \ " f # Á Ü ¼ # l F g " é ¶ _ [ jl y © ½ + É â Ä

º µ 1 Ï s { 9 # Q t · ú §Ü ¼ 9 s H z ´+ « >Ü ¼ Ð S X ÷ &% 3 (Fig. 4). " f \ P E $ Ý ¼\ _ ô Ç í& h o s Ð 8

Fig. 5. Output power of the fundamental beam(1064 nm) : The cavity length was adjusted to maximize the output power under different pump powers.

|

â Ä º 7 £ ¤, * 3 i ç F g _ [ jl q §& h ½ + É â Ä º\ ë ß & h ½ + Ë

. Fig. 2 (a)ü < (b) H x ° ú כ_ o\ @ /ô Ç c ß ¼l _

o; ¤ É r q 5 p w ¦, Ø ¦§ 4 Ö ¦(M

3

) \ " f_ c ß ¼l H (a) Ð

(b) ß ¼ 9, ì ø Í Ö ¦(M

1

) \ " f H (b) Ð (a) ì ø Í

&

h Ü ¼ Ð ß ¼> M ® o . ì ø Í Ö ¦ \ " f_ c ß ¼l H s 1 p q B

| 9

_ ¸× ¼& ñ ½ + Ë(mode matching)\ ' a > ÷ &# Q (a) (b)_

â

Ä º Ð 7 á § 8 Ä »o ¦ ^ ¦ Ã º e Ü ¼ , / B N l \ ¦ ½ ¨

$ í

l Ðî r ' a > Ð (b)_ ¸| ` ¦ × þ # Ø ¦§ 4 :

£ ¤$ í 1 p x` ¦ 8 £ ¤& ñ % i .

Fig. 3 É r 0 l qÒ o Y Us $ \ ¦ % 3 l 0 AK q + þ A & ñ ` ¦ / B N

l ? /Â Ò\ ¶ ú { 9 ô Ç ? /Â Ò/ B N l _ > h| Ä Ì ¸s . Fig. 1\ [ O

> ) a / B N l _ Ø ¦§ 4 Ö ¦(M

3

)` ¦ ] j ¦, 532 nmü <

1064 nm \ ¦ì ø Í ïh A ) a Ö ¦(M

4

) Ð @ /^ % i . Õ ª o

¦ ª \ 532 nmü < 1064 nm\ @ /K Á ºì ø Í ïh A ) a 3 × 3 × 5 mm

³

_ ] j27 á x 0 A © & ñ ½ + Ë KTP & ñ (Castech ]

j¾ ¡ §)` ¦ M

4

H % \ Z ~ ¦ 0 Au \ ¦ p [ j > ¸] X ½ + É Ã º e

¸2 ¤ s ß ¼ Ðp ' Â Ò Ã Ì ) a s 1 l x @ / 0 A\ [ O u % i .

¢

¸ô Ç Ø ¦§ 4 Ö ¦(M

2

) 6 £ § \ H l : r (1064 nm)\ ¦ ] j

¦ Å Ò Ã º C ) a 0 l qÒ oY Us $ _ Ø ¦§ 4 : £ ¤$ í ` ¦ 8 £ ¤& ñ l 0

AK 532 nm È Òõ 9 ' \ ¦ 6 x % i .

III. M Ä ] Ø õ m Í < g2w º 8 ý û s ÚI í Ä ¤V R Ë

s

1 p q B | 9 _ * 3 i ç M

1

\ " f E $ Ý ¼ L t _ o D 85 mm s ¦, L\ " f Ø ¦§ 4 Ö ¦ M

3

t _ o x 60 mm Fig. 1 õ ° ú É r - + þ A / B N l \ ¦ ½ ¨$ í # , * 3 i ç F g _ [ j l

? /% 3 . ì ø Í Ö ¦ 98 % Ø ¦§ 4 Ö ¦` ¦ 6 x % i ` ¦ â Ä

º 8.91 W [ jl _ * 3 i ç F g \ @ /K 1.25 W_ Ø ¦§ 4 ` ¦ % 3 # Q

(4)

Fig. 6. Output power of the SHG(532 nm) versus input power.

14.0 %_ þ j@ /Ø ¦§ 4 ´ òÖ ¦` ¦ % 3 % 3 ¦, Ø ¦§ 4 s y è l

t _ l Ö ¦ l ´ òÖ ¦ É r 16.7 %\ ¦ ? /% 3 . s M : µ 1 Ï

ë H) 3 ° ú כ É r 1.45 W% i . s 1 p q B | 9 _ \ P ´ òõ Ð K 9 W s © * 3 i ç | ¨ c M : Ø ¦§ 4 s / å L y y è < Ê` ¦ ^ ¦ Ã º e H X

<, z ´+ « > õ * 3 i ç F g _ [ jl 7 £ x | ¨ c Ã º2 ¤ þ j@ / Ø ¦§ 4 ` ¦

%

3 l 0 AK " f H / B N l U ´s 145 mm\ " f 110 mm t t

@

/K " f / B N l U ´s \ ¦ ¸] X # % 3 ` ¦ Ã º e H þ j@ /Ø ¦§ 4 _

õ \ ¦ Fig. 5 \ ? /% 3 . * 3 i ç F g _ [ jl 22.9 W{ 9 M : þ j@ / 3 W_ l : r Ø ¦§ 4 ` ¦ % 3 % 3 Ü ¼ 9, l Ö ¦ l ´ ò Ö

¦ É r 13.4 % Ð 8 £ ¤& ñ ÷ &% 3 .

Fig. 6 É r D = 85 mm, x = 60 mm{ 9 M : KTP q + þ A

& ñ ` ¦ s 6 x # ? /Â Ò/ B N l Å Ò Ã º C ) a ] j2 ¦ ¸ Ø

¦§ 4 : £ ¤$ í ` ¦ · p כ s 9 10.6 W Ð # l | ¨ c M : 130 mW [

jl \ ¦ t H 532 nm _ 0 l qÒ o Y Us $ \ ¦ % 3 ` ¦ Ã º e % 3 .

Fig. 7 õ Fig. 8 É r º ú ± ú (knife-edge)Z O ` ¦ s 6 x # ] j2 ¦

¸ _ c | 9 p ' ü < c µ 1 Ïí ß y ` ¦ S X ô Ç õ s 9, y

y M

²

= 1.90, θ = 9.95 mrad Ü ¼ Ð 8 £ ¤& ñ ÷ &% 3 .

IV. + s Ç Â ] Ø

F

g$ 3 Ä » ) a s ¸× ¼ Y Us $ \ ¦ * 3 i ç F g " é ¶ Ü ¼ Ð

H é ß # l Nd:YAG/KTP Y Us $ _ / B N l \ ¦ s 1 p q B

| 9

? /\ " f * 3 i ç F g \ _ ô Ç \ P E $ Ý ¼ ´ òõ \ ¦ ¦ 9 # ½ ¨$ í

¦ Õ ª Ø ¦§ 4 : £ ¤$ í ` ¦ 8 £ ¤& ñ % i .

*

3 i ç F g _ [ jl \ É r \ P E $ Ý ¼_ Ä »´ ò í& h o \ ¦ \ V 8

£

¤ ¦, s \ ¦ · û ª É r ½ ¨ E $ Ý ¼ Ð H r & ' § > =\ ¦

9 # º ¡ § Ü ¼ Ð+ Ð î ß & ñ & h / B N l _ U ´s \ ¦ ç ß é ß y

& ñ ½ + É Ã º e % 3 . / B N l _ U ´s \ ¦ 145 mm Ð ¦& ñ

Fig. 7. The beam quality factor M

²

of the Nd:YAG/KTP green laser.

Fig. 8. The beam divergence angle of the Nd:YAG/KTP green laser.

r

v ¦ * 3 i ç F g _ [ jl \ ¦ 7 £ x r ( ` ¦ M :, 9 W Â Ò H \ " f Ø

×

¼ Qf ` ¦ · ú Ã º e % 3 Ü ¼ 9, Ø ¦§ 4 s y è l t _ l Ö

¦ l ´ òÖ ¦ É r 16.7 % Ð ' a8 £ ¤ ÷ &% 3 . ¢ ¸, * 3 i ç F g _ [ jl

7 £

`

¦ % 3 # Q : r õ / B N l U ´s Â ú ª f ` ¦ S X ½ + É Ã º e % 3

. s M : * 3 i ç F g _ [ jl 22.9 W{ 9 M : þ j@ / 3 W_ l : r

(1064 nm) Ø ¦§ 4 ` ¦ % 3 % 3 Ü ¼ 9, l Ö ¦ l ´ òÖ ¦ É r 13.4 % Ð 8

£ ¤& ñ ÷ &% 3 . ¢ ¸ô Ç q + þ A & ñ KTP\ ¦ / B N l ? /Â Ò\

¶ ú

{ 9 ô Ç ? /Â Ò/ B N l Å Ò Ã º C ~ ½ Ód ` ¦ s 6 x # 10.6 W _

* 3 i ç F g \ " f 130 mW_ î ß & ñ ) a 0 l qÒ oY Us $ \ ¦ % 3 ` ¦ Ã º e

% 3 . s M : 0 l qÒ oY Us $ _ c | 9 p ' M

²

= 1.90, c µ

1 Ïí ß y θ = 9.95 mradÜ ¼ Ð 8 £ ¤& ñ ÷ &% 3 .

¦^ Y Us $ _ s 1 p q B | 9 \ " f 9 & h Ü ¼ Ð µ 1 ÏÒ q t÷ & H \ P s

´ òÖ ¦& h Ü ¼ Ð K è | ¨ c Ã º e ¸2 ¤ f . Ë 8\ ¦ > h r v ¦, Ð

(5)

Y

c p w Ã U Ø ô

[1] R. G. Smith, IEEE J. Quantum Electron. QE-6, 215 (1970).

[2] H. Hemmati and J. R. Lesh, Opt. Lett. 19, 1322 (1994).

[3] W. A. Clarkson, K. I. Martin and D. C. Hanna, in Conference on Lasers and Electro-Optics, 15 of OSA 1995 Technical Digest Series (Optical Society of America, Washington, D.C., 1995), paper CMD8.

and D. Ragazzi, Appl. Opt. 36, 597 (1997).

[9] Sungman Lee, J. Korean Phys. Soc. 43, 507 (2003).

[10] Won Kwon Jang and Seong Sook Shin, Sae Mulli 49, 253 (2004).

[11] M. E. Innocenzi, H. T. Yura, C. L. Fincher and R.

A. Fields, Appl. Phys. Lett. 56, 1831 (1990).

[12] A. E. Siegman, Lasers (University Science, Mill Val- ley, Calif., 1986).

Design and Output Characteristics of a Laser-Diode-Pumped Continuous-Wave Nd:YAG/KTP Green Laser

Cha Gon Park, Bum Soo Ahn, Han Tae Choo

^∗

and Gyu Ug Kim

School of Natural Science, Kumoh National Institute of Technology, Gyeongbuk 730-701 (Received 9 November 2006)

We designed a continuous-wave Nd:YAG/KTP green laser which had a thermal lens effect and was pumped by using a laser diode(LD) and we reported here results for its output characteristics.

The Nd:YAG laser, which is pumped by LD with a power of 22.9 W, emits as much as 3 W of output power at 1064 nm and has a slope efficiency of 13.4 %. Also, the intracavity frequency doubling obtained by using a potassium titanyl phosphate(KTP) nonlinear crystal generates green light at 532 nm. At an incident pumping power of 10.6 W, a SHG output power of 130 mW is achieved with a beam quality parameter of M

²

= 1.90 and beam divergence angle of θ = 9.95 mrad.

PACS numbers: 42.60.Pk, 42.65.Ky

Keywords: Nd:YAG/KTP green laser, Thermal lens effect, Nonlinear crystal, Intracavity frequency doubling

∗

E-mail: [email protected]

% i . Y Us $  s  ¸× ¼_ * 3 i ç Ø ¦§ 4 s 22.9 W{ 9 M : 3 W_ 1064 nm-Nd:YAG Y Us $ _ Ø ¦§ 4 ` ¦ % 3 % 3 Ü

/

B N  l \  ¦ s 1 p q B | 9  ? /\ " f_  * 3 i ç F g \  _ ô  Ç \ P E $ Ý ¼ ´ òõ \  ¦  ¦ 9 #  ½ ¨$ í  ¦ Õ ª Ø  ¦§ 4 : £ ¤$ í `  ¦ 8 £ ¤& ñ

% i  . Y Us $  s  ¸× ¼_  * 3 i ç Ø  ¦§ 4 s  22.9 W{ 9  M : 3 W_  1064 nm-Nd:YAG Y Us $ _  Ø  ¦§ 4 `  ¦ % 3 % 3  Ü

¼ 9, l Ö  ¦ l  ´ òÖ  ¦ É r 13.4 %  Ð 8 £ ¤& ñ ÷ &% 3  . ¢ ¸ô  Ç q   + þ A  & ñ   KTP(potassium titanyl phosphate)\  ¦ /

B N  l  ? /Â Ò\  ¶ ú { 9 ô  Ç ? /Â Ò/ B N  l  Å Ò Ã º C  ~ ½ Ód  Ü ¼ Ð * 3 i ç Ø  ¦§ 4 s  10.6 W{ 9  M :, 130 mW_  î ß & ñ

 )

a 0 l qÒ  oY Us $ \  ¦ % 3 `  ¦ Ã º e  % 3  . s M : 0 l qÒ  oY Us $ _  c  | 9   p '  M

= 1.90, c   µ 1 Ïí ß y   θ = 9.95 mrad Ü ¼ Ð 8 £ ¤& ñ ÷ &% 3  .

PACS numbers: 42.60.Pk, 42.65.Ky

Keywords: Nd:YAG/KTP 0 l qÒ  oY Us $ , \ P E $ Ý ¼ ´ òõ , q   + þ A   & ñ , ? /Â Ò/ B N  l  Å Ò Ã º C 

I. " e Â ] Ø

s  ¸× ¼ Y Us $   H  ¦^ Y Us $ _  * 3 i ç F g " é ¶ Ü ¼ Ð  6 x

÷

&  " f  Ð     ¦ ´ òÖ  ¦& h   / B N  l  [ O > \  ¦ 0 p x >  Ù þ ¡

.    ¦Ø  ¦§ 4 s  ¸× ¼ Y Us $   H l  > r _  s  : r Y Us 

$

\  ¦ @ /  K  W 1 ¸n ¶ o u(Nd) > \ P   ¦^ Y Us $ _  * 3 i ç F g

"

é

¶ Ü ¼ Ð  6 x ÷ &  " f ? /Â Ò/ B N  l \  ¦ s 6 x ô  Ç Å Ò Ã º C  ~ ½ Ó d 

[1]\  _ K  3 W & ñ  ¸\  K { © ÷ &  H   5 Å q µ 1 Ï  0 l qÒ  o Y Us 

$

\  ¦ % 3 l  ¸ Ù þ ¡  [2,3]. ¢ ¸ þ j   H \   H 946 nm\  ¦   1 l x Ã º C

r   ' õ AÒ  oY Us $ \   ' a ô  Ç   ½ ¨\ " f 473 nm_   © 

\

" f 1.25 W [4], 457 nm\ " f  H 4.6 W [5] _   ¦Ø  ¦§ 4 `  ¦

%

3 # Q · p  כ Ü ¼ Ð  Ð ¦÷ &% 3  . s  Qô  Ç  ¦Ø  ¦§ 4  ¦^ Y Us $ 



 H * 3 i ç s  s À Ò# Qt   H 1 l x î ß  s 1 p q B | 9 \ " f  H * 3 i ç F g \  _

ô  Ç f  ¨ Ã º { 9 # Q >  ÷ & 9, Y Us $  Ø  ¦§ 4 õ  / B N  l   < H z

´`  ¦ ] jü @ô  Ç  Qt   H \ P  Ð   ¨ 8  ) a .   ¨ 8  ) a \ P  É r Í  ty   s

 s À Ò# Qt   H B | 9 ³ ð  Ü ¼ Ð S X  í ß ÷ & ¦, s M : B | 9  ? /Â Ò

\

" f  H Ô  ¦ç  H{ 9 ô  Ç  : r  ¸ì  r  í Ò q tl >   ) a . s    : r  ¸ì  r



í_  q ç  H| 9 $ í  É r B | 9 _  Ï ã J] X Ò  ¦ õ  \ P Ø   ½ Ó`  ¦ / B N ç ß & h Ü ¼ Ð

Ø Ô>  ë ß [ þ t # Q \ P E $ Ý ¼(thermal lens)  & ³ ©  [6]s   \ P 4  ¤ Ï

ã J] X (thermal birefringence)  & ³ ©  [7] 1 p x`  ¦ { 9 Ü ¼  . ¢ ¸ ô

 Ç / B N  l  ? /Â Ò_   ¸× ¼ ß ¼l _    o  H s 1 p q B | 9 s   q 



 + þ A   & ñ \ " f_   ¸× ¼ & ñ ½ + Ë(mode matching)\  % ò  ¾ Ó`  ¦ º

¡

§ É r Ó ü t : r, / B N  l _  p  èô  Ç U ´s   o\  Ø  ¦§ 4 s    y   

>

   ½ + É Ã º e    [8]. s ü < ° ú  É r  & ³ ©  É r # l  F g _  [ jl 

E-mail: [email protected]

 7 £ x ½ + ÉÃ º2  ¤  8¹ ¡ ¤ Ì º§ Â K t  9,   " f  ¦Ø  ¦§ 4 ] j2 ¦ ¸

(Second Harmonic Generation, SHG)\  ¦ % 3   H X < e  # Q Û

 ¦ # Q  ½ + É ×  æ כ ¹ô  Ç õ ] j ÷ & ¦ e   .

\ P

% ò  ¾ Ó`  ¦ ×  ¦ s l  0 Aô  Ç @ /³ ð& h   \ V Ð  H  Ð © 6 x E $ Ý ¼

\

 ¦ ¶ ú { 9     [9], λ/4-ó ø Í`  ¦ s 6 x ô  Ç \ P 4  ¤Ï ã J] X   & ³ © _   Ð



©  [10] Õ ªo  ¦ Nd

 '  ÷ &t  · ú § É r YAG\  ¦ Nd:YAG

 

& ñ  ª A á ¤ \  · ¡ ­ #  Å Ò  H 1 p x [4]  ª ô  Ç r  ¸ s À Ò# Qt  ¦ e 

 .



: r   ½ ¨\ " f  H s  ¸× ¼ Y Us $  Ð 7 á x* 3 i ç ÷ &  H -   + þ

A Nd:YAG Y Us $  / B N  l \  ¦ [ O >   ¦ ½ ¨  \ P E $ Ý ¼ ´ ò õ

(spherical thermal lens effect)\  ¦  ¦ 9ô  Ç ABCD  

'  § > =(transfer matrix)`  ¦ s 6 x K  s 1 p q B | 9 õ  q   + þ A  

&

ñ (nonlinear crystal)\ " f_  c   ß ¼l \  ¦ > í ß K  4  § Ü ¼ Ð+ 

\ P

E $ Ý ¼ ´ òõ  c    ¸× ¼   o\  p u   H % ò  ¾ Ó`  ¦ · ú   Ð  ¤ Ü

¼ 9, \ P E $ Ý ¼ ´ òõ \   Ð  W =    y  ô  Ç / B N  l \  ¦ ½ ¨$ í 



¦  % i  . s ü < ° ú  É r / B N  l  ½ ¨ ¸\ " f l  : r (1064 nm) _  Ø  ¦§ 4 õ  l Ö  ¦ l  ´ òÖ  ¦(slope efficiency)`  ¦ 8 £ ¤& ñ 

%

i Ü ¼ 9, ? /Â Ò/ B N  l    1 l x Ã º C (intracavity frequency doubling) ~ ½ Ód  `  ¦ s 6 x #  532 nm_  0 l qÒ  o Y Us $ \  ¦ % 3 

%

3  . s M : * 3 i ç F g _  [ jl \    É r 0 l qÒ  o Y Us $ _  Ø  ¦§ 4 , c 

| 9   p '  (beam quality parameter, M

) x 9 µ 1 Ïí ß  y



% i . Y Us $ s ¸× ¼_ * 3 i ç Ø ¦§ 4 s 22.9 W{ 9 M : 3 W_ 1064 nm-Nd:YAG Y Us $ _ Ø ¦§ 4 ` ¦ % 3 % 3 Ü

B N l \ ¦ s 1 p q B | 9 ? /\ " f_ * 3 i ç F g \ _ ô Ç \ P E $ Ý ¼ ´ òõ \ ¦ ¦ 9 # ½ ¨$ í ¦ Õ ª Ø ¦§ 4 : £ ¤$ í ` ¦ 8 £ ¤& ñ

% i . Y Us $ s ¸× ¼_ * 3 i ç Ø ¦§ 4 s 22.9 W{ 9 M : 3 W_ 1064 nm-Nd:YAG Y Us $ _ Ø ¦§ 4 ` ¦ % 3 % 3 Ü

¼ 9, l Ö ¦ l ´ òÖ ¦ É r 13.4 % Ð 8 £ ¤& ñ ÷ &% 3 . ¢ ¸ô Ç q + þ A & ñ KTP(potassium titanyl phosphate)\ ¦ /

B N l ? /Â Ò\ ¶ ú { 9 ô Ç ? /Â Ò/ B N l Å Ò Ã º C ~ ½ Ód Ü ¼ Ð * 3 i ç Ø ¦§ 4 s 10.6 W{ 9 M :, 130 mW_ î ß & ñ

)

a 0 l qÒ oY Us $ \ ¦ % 3 ` ¦ Ã º e % 3 . s M : 0 l qÒ oY Us $ _ c | 9 p ' M

= 1.90, c µ 1 Ïí ß y θ = 9.95 mrad Ü ¼ Ð 8 £ ¤& ñ ÷ &% 3 .

Keywords: Nd:YAG/KTP 0 l qÒ oY Us $ , \ P E $ Ý ¼ ´ òõ , q + þ A & ñ , ? /Â Ò/ B N l Å Ò Ã º C

s ¸× ¼ Y Us $ H ¦^ Y Us $ _ * 3 i ç F g " é ¶ Ü ¼ Ð 6 x

& " f Ð ¦ ´ òÖ ¦& h / B N l [ O > \ ¦ 0 p x > Ù þ ¡

. ¦Ø ¦§ 4 s ¸× ¼ Y Us $ H l > r _ s : r Y Us

\ ¦ @ / K W 1 ¸n ¶ o u(Nd) > \ P ¦^ Y Us $ _ * 3 i ç F g

¶ Ü ¼ Ð 6 x ÷ & " f ? /Â Ò/ B N l \ ¦ s 6 x ô Ç Å Ò Ã º C ~ ½ Ó d

[1]\ _ K 3 W & ñ ¸\ K { © ÷ & H 5 Å q µ 1 Ï 0 l qÒ o Y Us

\ ¦ % 3 l ¸ Ù þ ¡ [2,3]. ¢ ¸ þ j H \ H 946 nm\ ¦ 1 l x Ã º C

r ' õ AÒ oY Us $ \ ' a ô Ç ½ ¨\ " f 473 nm_ ©

" f 1.25 W [4], 457 nm\ " f H 4.6 W [5] _ ¦Ø ¦§ 4 ` ¦

3 # Q · p כ Ü ¼ Ð Ð ¦÷ &% 3 . s Qô Ç ¦Ø ¦§ 4 ¦^ Y Us $

H * 3 i ç s s À Ò# Qt H 1 l x î ß s 1 p q B | 9 \ " f H * 3 i ç F g \ _

ô Ç f ¨ Ã º { 9 # Q > ÷ & 9, Y Us $ Ø ¦§ 4 õ / B N l < H z

´` ¦ ] jü @ô Ç Qt H \ P Ð ¨ 8 ) a . ¨ 8 ) a \ P É r Í ty s

s À Ò# Qt H B | 9 ³ ð Ü ¼ Ð S X í ß ÷ & ¦, s M : B | 9 ? /Â Ò

" f H Ô ¦ç H{ 9 ô Ç : r ¸ì r í Ò q tl > ) a . s : r ¸ì r

í_ q ç H| 9 $ í É r B | 9 _ Ï ã J] X Ò ¦ õ \ P Ø ½ Ó` ¦ / B N ç ß & h Ü ¼ Ð

Ø Ô> ë ß [ þ t # Q \ P E $ Ý ¼(thermal lens) & ³ © [6]s \ P 4 ¤ Ï

ã J] X (thermal birefringence) & ³ © [7] 1 p x` ¦ { 9 Ü ¼ . ¢ ¸ ô

Ç / B N l ? /Â Ò_ ¸× ¼ ß ¼l _ o H s 1 p q B | 9 s q

+ þ A & ñ \ " f_ ¸× ¼ & ñ ½ + Ë(mode matching)\ % ò ¾ Ó` ¦ º

§ É r Ó ü t : r, / B N l _ p èô Ç U ´s o\ Ø ¦§ 4 s y

½ + É Ã º e [8]. s ü < ° ú É r & ³ © É r # l F g _ [ jl

7 £ x ½ + ÉÃ º2 ¤ 8¹ ¡ ¤ Ì º§ Â K t 9, " f ¦Ø ¦§ 4 ] j2 ¦ ¸

(Second Harmonic Generation, SHG)\ ¦ % 3 H X < e # Q Û

¦ # Q ½ + É × æ כ ¹ô Ç õ ] j ÷ & ¦ e .

% ò ¾ Ó` ¦ × ¦ s l 0 Aô Ç @ /³ ð& h \ V Ð H Ð © 6 x E $ Ý ¼

¦ ¶ ú { 9 [9], λ/4-ó ø Í` ¦ s 6 x ô Ç \ P 4 ¤Ï ã J] X & ³ © _ Ð

© [10] Õ ªo ¦ Nd

' ÷ &t · ú § É r YAG\ ¦ Nd:YAG

& ñ ª A á ¤ \ · ¡ # Å Ò H 1 p x [4] ª ô Ç r ¸ s À Ò# Qt ¦ e

.

: r ½ ¨\ " f H s ¸× ¼ Y Us $ Ð 7 á x* 3 i ç ÷ & H - + þ

A Nd:YAG Y Us $ / B N l \ ¦ [ O > ¦ ½ ¨ \ P E $ Ý ¼ ´ ò õ

(spherical thermal lens effect)\ ¦ ¦ 9ô Ç ABCD

' § > =(transfer matrix)` ¦ s 6 x K s 1 p q B | 9 õ q + þ A

ñ (nonlinear crystal)\ " f_ c ß ¼l \ ¦ > í ß K 4 § Ü ¼ Ð+

E $ Ý ¼ ´ òõ c ¸× ¼ o\ p u H % ò ¾ Ó` ¦ · ú Ð ¤ Ü

¼ 9, \ P E $ Ý ¼ ´ òõ \ Ð W = y ô Ç / B N l \ ¦ ½ ¨$ í

¦ % i . s ü < ° ú É r / B N l ½ ¨ ¸\ " f l : r (1064 nm) _ Ø ¦§ 4 õ l Ö ¦ l ´ òÖ ¦(slope efficiency)` ¦ 8 £ ¤& ñ

i Ü ¼ 9, ? /Â Ò/ B N l 1 l x Ã º C (intracavity frequency doubling) ~ ½ Ód ` ¦ s 6 x # 532 nm_ 0 l qÒ o Y Us $ \ ¦ % 3

3 . s M : * 3 i ç F g _ [ jl \ É r 0 l qÒ o Y Us $ _ Ø ¦§ 4 , c

| 9 p ' (beam quality parameter, M

) x 9 µ 1 Ïí ß y

(divergence angle)` ¦ 8 £ ¤& ñ % i .

II. «à Ã ÅM º

Fig. 1 \ H Y Us $ s ¸× ¼ Ð * 3 i ç H Nd:YAG Y U s

$ _ / B N l ½ ¨ ¸\ ¦ ? /% 3 . ï# Q t 2 £ § s 400 µm,

h½ ¨Ã º(numerical aperture, NA) 0.22 F g$ 3 Ä »

+ Ë ) a s ¸× ¼ Y Us $ (fiber coupled LD, Limo Laser Sys- tem, 808 nm)\ ¦ q ½ ¨ E $ Ý ¼ ¸½ + Ë(aspheric lens pair, f = 11.0 mm, NA = 0.25, AR coated at 600 ∼ 1050 nm)` ¦ :

x K s 1 p q B | 9 Ð | 9 5 Å q r ( . Nd

1.1 at.% ' ) a f

â 3 mm, U ´s 5 mm s 1 p q B | 9 Nd:YAG & ñ É r * 3 i ç

(M

) s 808 nm\ @ /K ¦È Òõ ÷ & ¦ 1064 nm x 9 532 nm \ @ /K " f H ¦ì ø Í ÷ & ¸2 ¤ ïh A÷ &% 3 Ü ¼ 9, É r É r 1064 nm \ @ /K Á ºì ø Í ÷ & ¸2 ¤ ïh A % i . 45

Ð , # Q

¨ î Ö ¦ M

H 1064 nm \ @ /K ¦ì ø Í , 532 nm\

/K 95 % s © È Òõ ÷ & ¸2 ¤ s Ò o ïh A % i . E $ Ý ¼ L É r 1064 nm ü < 532 nm_ © ¸¿ º Á ºì ø Í ïh Aô Ç ^ ¦2 ¤-¨ î

E $ Ý ¼ Ð í& h o 60 mms . 1064 nm\ @ /K 2

% _ È Òõ Ö ¦` ¦ Ø ¦§ 4 Ö ¦(M

)` ¦ 6 x # l : r _ Ø

¦§ 4 ` ¦ Molectron _ Ø ¦§ 4 > (Power Max 5100, probe : PM10) Ð S X % i . s M : s 1 p q B | 9 É r # l F g _ f ¨ Ã º

Ð K µ 1 ÏÒ q t ) a \ P s ´ òÖ ¦& h Ü ¼ Ð K è | ¨ c Ã º e ¸2 ¤ ´ o u

í{ 9 Ð y ø ß 6 £ § · ú À Òp ³ o u f . Ë 8\ ¦& ñ r & , ½ ` ¦ s 6 x K

Í ty r ( . s H \ P è \ ¦ s 6 x ô Ç ~ ½ Ód s Ã ºÍ t d

Ð Õ ª t ´ òÖ ¦& h s t H · ú §Ü ¼ , / B N l _ U ´s

´t · ú § É r ' a > Ð Â Ò1 p q s 2 [ô Ç ~ ½ Ód s .

M. E. Innocenzi 1 p x _ õ [11]\ Ø Ô , s 1 p q B | 9 \

f µ 1 ÏÒ q t÷ & H \ P E $ Ý ¼ ´ òõ \ _ ô Ç Ä »´ ò í& h o H f

) a .

l " f w