What are the literary techniques found in "The New Colossus"?

"The New Colossus" is what's called a Petrarchan sonnet consisting of fourteen lines with a rhyme scheme of abbaabba in the octet, and cdcdcd in the sestet. In keeping with sonnets of this type, there is a volta, or turn, between octet and sestet. This represents the moment at which there is a slight change in the prevailing thought or argument, leading ultimately to a resolution of the poem's "problem." In the sestet Lazarus...

"The New Colossus" is what's called a Petrarchan sonnet consisting of fourteen lines with a rhyme scheme of abbaabba in the octet, and cdcdcd in the sestet. In keeping with sonnets of this type, there is a volta, or turn, between octet and sestet. This represents the moment at which there is a slight change in the prevailing thought or argument, leading ultimately to a resolution of the poem's "problem." In the sestet Lazarus contrasts the statue and the hopeful message it proclaims with the monstrous expression of power represented by the Colossus of Rhodes in the first two lines. This new colossus is not like the colossus of old, just as the New World is far removed from the ancient.

Lazarus uses alliteration and assonance to emphasize important lines in the poem. They're particularly useful techniques because they draw attention to themselves, causing us to focus on what's being said. For example:

"sea-washed, sunset gates shall stand . . ." 

Here, the 's' sounds show alliteration; the 'a' sounds assonance.

We are left in no doubt as to the idealized portrayal of the Statue of Liberty being given here. Here are some more examples:

"Glows world-wide welcome;"

Alliteration is used here to draw our attention to the bright shining image of Liberty and the welcome it represents to new immigrants.

The poem is written in iambic pentameter, which gives it a slow, stately rhythm, in keeping with its high moral tone. The combination of this poetic meter with a profusion of vowel sounds in lines 11 and 12 conveys a wave-like motion, like the waves that will bring immigrants to America's shores:

"Your huddled masses yearning to breathe free,
The wretched refuse of your teeming shore."