l6.
3 Vaishnavi A
ypes of lasers (QspGPga4)
C. Raman Lasers
Baman Fiber Lasers (RFLs)
Raman Fiber Lasos (RF1S) tperate on the principle ct,
Stimulated Rarnan dtering (sks)
Stimulatod Rarnan Scatterfng (cRs) is a nonlinear
bptica process where a pump photon interact s with
madium, transfering eroqy to genrate a lower
energy 9ignal photon.
1t 0cc urs hen a high. frequency pump photon(hyp)
and a lower - frequency atqnal phstn (hvs) erar a
non-linear optieal mediun, uch as an optiad ber
The slgnal photon simuletes the emies ion of
another photn by stokes - Shifting the punp phot ong
energ
This result in aa signal phctun uhse
frecyuency
matches that t the input signal phcten, uhia
tha exCOSS energy from the pump photon s
trans fexd to the vibraticnal modes f te mediur
Sps fs a third- order nonunear optial procoss, which
means,its eficienty depets n tte properties cptíal matium.
Aniq ior (eray
The opicd qun of n Taman ibt
Jovetne d by the Rarnan
the ndwidthof Raman aaio i detoamined
ku th vibaationd sctun Gf
of the glas hot
tor Conveting RFA into n RFL. t req,uires
ceical focdback, achive dtraough iber Brag9
gatings (FeBac)
FBGrS defíne a iescnator that Support tscillation
at speciFic icquency chen Yeqlectana is high
Aistributed- eedback (DFB) esonat ors can ao
be used instead of FBGS
Osci llatin frequency Ys jis oer than the pup
rocyuencY Vp by a stotes ghit Ve
The stotes shi (VR) denat an the vibratim
proper tios of the host mat orial
Eibgr imple rsentatfon brought Rarman tehnoiegy to
the fore for Severa Yeans
Fiber lengths are long, hich provides higher
gain.
* Fibers have a Small Core diameter, which
Suppots strong light intera ctfon.
utin utvelnth cotot
eronission,o
pendatin nsion and timutat ed
in an 09sontl wa
Cascaded foman ber lasers
is tha th
Atuniue fatucs 6 fhrmn irteraction
shiyt te indapendent og the purnp teqyuny
Can act as a
The ist- oxder Raman. Shttod ight
dor the next - G6dor 3tokes Shipt
pump
Aesmator uxing a pair f ibor Bag gratngs ( FeG1)
lase. Thus lase
gcnerata the irst- 6rder Raman
ats as a þump i the nemt Raman sheft
Gocond- order ocilation s aeate d uuking a second
Then
Frbea Bragg Grating (tBG2).
Thi carading e$ect Continus, genenates multipl.
Tarnan hetot avelgenth.
hv
h
hvpo
hvpi
he
shis GA
Gf mutiple
multiple orders .
a) Ca scaded stokes
Phosphosiucate fiber
Aoubled clad
Y3 Siuafiber
Fe&
12 39 14g4 1239
1064 (06 4 100 50 l00%
l60%
I-pumplaser Raman wave length shifter
lase
b) Schermate of a Ramn phosphosii cate - fiber
ffber as
a double - clad Y53doped (ca
Punp sour. Pumped by a laser - dicde aNay.
tho
FB65 Yeglect Specific Ramn lase outpt
Continue nested pairs a FB s,
the Cscade can
using
until determined by the use n
utpud Couple that
diects Lght tut 0f the fiber t the desired frequenty .
Raman fibee tsew Comprising mltplk ovdes stoka
thus otter a qeatly expanded range o poscble
Shits thw
waveleng ths eund knoun as Chscaded Raman fber lasas
optial Pei o Raman ber aQu nn oa ch
hundied a9cntts
nt s uwing advanod Cngigution, uch
s see t lacis in Combipetn uth Ramn fiba ampiners
bptical powes (an be inrea sQd to the Poulirw reqime
hy empleying mixed
mixcd ae-rth (o) Rarman ampiiction
in ybt. oped fbeu.
lyHerbium
Rarnan deben lases are usefal r mny pplicatins,
1. Jaser pmping
2. cptical fibou Ceromuricatfom
3 Super Contiruum qenera tÉ m
4. Matenal Procesing
5.clinical medfcine
They partteulary suitable tor pumping Raman
ihen amptipieu în
xponso ave length ivisiom. multiplexed (DWS)
Remote pumping erbium ded fiber amnpleier s
ntvaned desiqns
Ultra - low thresheld , iqh- eficienc y, siqle
node cw Ramo fiber laseTs Fabricated în ulra - hfoh.
torotal silca microcavi ies
The most attractive feature aa RFL is that oscilatton
Ver a brad range of wnve lengths is Supported by
"pump uiavelength
Fher materla!
" Fiber Bragg gratings.
sAimulated Brfllouin Snttertng (aBS):
It Can be sed in an analsgou wny to
Cons truct Brilloun ffber lasers
bilouin frea,ue ncy shit and band width
The
are inn the vicinity bt 10 GHz and
t7or aflica fbes
Theae Vaues Ne Grdes c
des oh maqníde lower thn
Ramn Grequency ghit and
thse or the ame mateLial.
bandoiAth the
